Nagase Analbuminemic Rats Research Articles

Estrogen effects on triglyceride metabolism in analbuminemic rats

Triglyceride (TG) levels are normally lower in female rats, while the opposite is the case in the Nagase analbuminemic rats (NAR). Increased TG levels in normal males are caused by a testosterone-mediated decrease in postheparin (PH) lipoprotein lipase (LpL). Castration of males reduces TG, while castration of females is without effect. TG levels are reduced by castration of the female NAR, suggesting that estrogen rather than testosterone causes hypertriglyceridemia in this strain. The mechanism for this increase is unknown. We measured secretion of very-low density lipoprotein (VLDL) TG using Triton WR 1339 clearance as the disappearance from blood of 3H-trioleate and 14C-cholesterol-labeled chylomicrons (CM), and the activity of the PH lipases: LpL and hepatic lipase (HL). All were determined in Sprague-Dawley (SD) and NAR female, male, and ovariectomized (OVX) rats. TG levels were significantly greater in female NAR in comparison to all other groups. Ovariectomy of NAR significantly ameliorated hypertriglyceridemia. VLDL TG secretion was significantly greater in intact female NAR compared with all other groups. There were no other differences in VLDL TG secretion among the other groups. The clearance of CM was greatest in female SD rats, and OVX had no effect. NAR cleared CM less well than did SD rats (P < 0.001), but among NAR, clearance was greatest in OVX NAR and male NAR (P < 0. 002). Both PH LpL activity and HL activity were lowest in female NAR (P < 0.05). Ovariectomy partially corrected the defect in HL (P < 0. 05). TG levels in female NAR are in part a result of increased VLDL-TG secretion, an effect mediated by estrogen. The presence of an estrogen-mediated catabolic defect that was alleviated by OVX was also observed. This catabolic defect is likely a result of an estrogen-mediated decrease both in LpL and HL expressed only in the presence of analbuminemia.

Early mechanisms of renal injury in hypercholesterolemic or hypertriglyceridemic rats.

Hyperlipidemia in conjunction with uninephrectomy leads to renal injury in rats. It is unknown whether this is due to mesangial cell or podocyte injury and whether the injuries induced by hypercholesterolemia and hypertriglyceridemia share a similar pathogenesis. Therefore, renal effects of hypercholesterolemia were studied in male rats with dietary hypercholesterolemia compared with rats on a regular diet. Renal effects of hypertriglyceridemia were studied in female Nagase analbuminemic rats (NAR). Hypertriglyceridemia was reduced in NAR by ovariectomy. Both models were studied after uninephrectomy or sham operation. Dietary hypercholesterolemia had little effect on plasma triglycerides, whereas ovariectomy in the NAR had no effect on plasma cholesterol. However, an increase in intermediate density lipoprotein cholesterol was common to both models. Dietary hypercholesterolemia and uninephrectomy separately induced a similar increase in proteinuria after 13 wk, which was additive when these interventions were combined. At this stage, only a minimal increase was present in glomerular alpha-smooth muscle actin staining, a marker of mesangial cell activation, or in mesangial matrix expansion. Moreover, platelet-derived growth factor-B chain, a marker of mesangial cell proliferation, was not increased. However, podocyte injury was prominent as evidenced by podocytic de novo expression of desmin and ultrastructural changes. Glomerular macrophage counts were increased by hypercholesterolemia but not by uninephrectomy, and were not related to the level of proteinuria. Hypertriglyceridemia and uninephrectomy in female NAR induced an increase in proteinuria after 24 wk, which was also associated with an increase in podocyte desmin expression without any mesangial activation and proliferation or matrix accumulation. Hypertriglyceridemia, proteinuria, and the increase in desmin staining were largely prevented by ovariectomy. Interstitial myofibroblast activation and tubulointerstitial injury accompanied proteinuria in both models. These findings indicate that both hypercholesterolemia and hypertriglyceridemia aggravate renal injury primarily via podocyte rather than via mesangial cell damage. Such podocyte injury is accompanied by tubulointerstitial cell activation and injury.

Coordinate augmentation in expression of genes encoding transcription factors and liver secretory proteins in hypo-oncotic states

In the nephrotic syndrome (NS) proteins of intermediate size (40 to 200 kD) are lost into the urine resulting in a decrease in plasma albumin concentration and as a consequence a reduction in plasma colloid osmotic pressure (pi). Plasma pi has also been reported to be reduced in the condition of hereditary analbuminemia. The liver, in an apparent compensatory response, increases synthesis of a group of secreted proteins defending plasma pi. Regulation of several of these proteins, including both positive and negative acute phase proteins, is at the transcriptional level. This is the only known condition in which transcription of both positive and negative acute phase proteins (APPs) are increased simultaneously. The specific transcription factor(s) that might regulate this cascade is not defined. RNA was extracted from livers of 5 rats with hereditary analbuminemia (the Nagase analbuminemic rat, NAR), 5 rats with NS induced by adriamycin (Adria), 5 rats with NS caused by passive Heymann nephritis (NS) and 5 control animals. The concentrations of mRNAs encoding four secreted proteins (albumin, transferrin, fibrinogen, and apo A-1), five transcription factors, early growth response factor 1 (EGRF-1), HNF-4, NGFI-C, EGR-3, and Krox20 relative to two housekeeping genes, beta actin and GAPDH were determined simultaneously using kinetic reverse transcriptase polymerase chain methodology (kRT-PCR). The levels of all mRNAs encoding secreted proteins except for albumin (which was reduced in NAR) were increased in NS and NAR and correlated significantly with one another. mRNA encoding EGRF 1 was increased fivefold in NS and NAR, and correlated significantly with mRNAs encoding Apo A-1, transferrin and albumin in the two NS groups. HNF-4 mRNA was increased approximately twofold in both NS groups and correlated with albumin (R = 0.881, P < 0.001), transferrin (R = 0.563, P = 0.012) and apo A-1 (R = 0.644, P = 0. 003). While fibrinogen mRNA correlated with that of each of the other secreted proteins, it did not correlate with either HNF-4 or EGRF-1 mRNA. Krox20, EGR3 and NGF1C were expressed at nearly undetectable levels. The hepatic response in conditions characterized by reduced plasma pi include increased levels of mRNAs encoding a group of secreted proteins, including the negative APPs albumin, transferrin and apo A-1, and the positive APP fibrinogen. Levels of mRNAs encoding negative APPs and fibrinogen correlate with one another, suggesting that they are coordinately controlled. Both EGRF-1 and HNF-4 may regulate the expression of the negative APPs, which have increased transcription in hypo-oncotic states.

Prolonged Function of Hepatocytes Transplanted into the Spleens of Nagase Analbuminemic Rats

Hepatocytes isolated from F344 rats were transplanted into the spleens of congenic Nagase analbuminemic rats (NARs). The morphology and function of the transplanted hepatocytes were investigated after 18 months. The hepatocytes had formed nodules that occupied approximately 35% of the area of the splenic parenchyma on microscopic examination. Ultrastructural examination demonstrated that the organelles of the transplanted cells were indistinguishable from those of normal hepatocytes. The serum albumin level in NARs at 18 months after intrasplenic transplantation (HCTx) was about 3.6 % of that in normal rats. We confirmed that the hepatocytes in the spleen produced albumin and increased the serum albumin level in NARs with HCTx. The NAR model demonstrates the effect of HCTx and prolonged changes in the morphology of the hepatized spleen.

Rapid clearance of transplanted hepatocytes from pulmonary capillaries in rats indicates a wide safety margin of liver repopulation and the potential of using surrogate albumin particles for safety analysis

Background/Aims: Applications of liver repopulation by hepatocyte transplantation require analysis of cell biodistributions, particularly when portasystemic shunting coexists. The aims of this study were to determine the fate of hepatocytes transplanted into the pulmonary vascular bed and to examine whether cell biodistributions could be approximated by convenient surrogates.Methods: Rat hepatocytes and macroaggregated serum albumin particles of similar sizes were injected into the portal and pulmonary vascular beds of rats, followed by biodistribution, survival and function analyses.Results: Although functionally intact, virtually all hepatocyteswere cleared from the pulmonary capillaries within 24 h. Serum albumin levels increased minimally in Nagase analbuminemic rats with or without portacaval shunting to enhance delivery of portal factors to transplanted cells in lungs. Despite intravenous injection of hepatocytes approaching >1×109 cells in humans, the hemodynamic changes were limited to transient increases in right atrial pressures. The hepatocyte distributions in specific vascular beds were largely reproduced by macroaggregated human serum albumin particles.Conclusions: Incidental intrapulmonary cell translocations during liver repopulation will have a wide safety margin. Use of macroaggregated serum albumin particles as surrogates for initial short-term biodistribution and safety analysis will advance hepatocyte transplantation, as the cost of GLP-certified laboratories and consumption of scarce donor livers will be avoided.

Substrate specificity of lysophospholipase D which produces bioactive lysophosphatidic acids in rat plasma

Previously we reported that lysophospholipase D in rat plasma hydrolyzes endogenous unsaturated lysophosphatidylcholines (LPCs) preferentially to saturated LPCs to lysophosphatidic acids with growth factor-like and hormone-like activities. In this study, we examined the possibility that association of LPCs with different proteins in rat plasma has an effect on the preference of lysophospholipase D for unsaturated LPCs. Large portions of various LPCs were found to be recovered in the lipoprotein-poor bottom fraction. Furthermore, the percentages of LPCs associated with albumin isolated from rat plasma were shown not to be consistent with their percentage conversions to lysophosphatidic acids by lysophospholipase D on incubation of rat plasma at 37°C. These results indicate that distinct distributions of LPCs in the plasma protein fractions are not critical factors for the substrate specificity of lysophospholipase D. Experiments with Nagase analbuminemic rats suggested that albumin–LPC complexes are not necessarily required for the hydrolysis by lysophospholipase D; lipoprotein-associate LPCs appeared to be good substrates for the phospholipase. We found that both saturated and unsaturated LPCs are present mainly as 1-acyl isomers in rat plasma. This result indicates that the preference of lysophospholipase D for unsaturated LPCs is not attributable to a difference in position of the acyl group attached to the glycerol backbone of LPC. In addition, lysophospholipase D was also found to attack choline phospholipids with a long chain group and a short chain alkyl group, although their percentage hydrolyses were low. Taken altogether, these results suggest that lysophospholipase D shows higher affinities for free forms of unsaturated acyl type LPCs equilibrated with albumin-bound and lipoprotein-associated forms, than for free forms of saturated acyl type LPCs and analogs of platelet-activating factor.

Suppression of the 5′ Splice Site Mutation in the Nagase Analbuminemic Rat with Mutated U1snRNA

Nagase analbuminemic rats (NAR) are deficient in serum albumin due to skipping of the albumin exon H caused by a mutation in the intron HI. This mutation deletes nucleotides from +5 to +11 in the 5′ splice site region, where it interacts with U1snRNA. To determine whether the mutation can be suppressed by the compensatory base substitution in U1snRNA, we constructed mutated U1snRNA genes with various degrees of complementarity to the mutated 5′ splice site. Several mutated U1snRNA genes activated the mutated 5′ splice site of the intron HI, when cotransfected with the albumin minigene derived from NAR.In vivoactivity of these mutated U1snRNAs correlated well with the predicted thermodynamic stability. Since mutation in the 5′ splice site is one of common causes of genetic defects in human (5), these data indicate that NAR is a good model system to examine the possibility of gene therapy using a mutated U1snRNA.

Bile acid metabolism in analbuminemic rats.

The bile acid concentrations in the serum, liver, bile, intestines, and feces of 3- and 19-mon-old male and female Nagase analbuminemic (NA) rats were compared with those in Sprague-Dawley (SD) rats. There was no significant difference in the bile acid levels between NA and SD rats. However, increased biosynthesis and pool size of cholic acid (CD) derivatives and decreased levels of chenodeoxycholic acid (CDCA) derivatives (increased CA/CDCA ratio) were detected in male NA rats as compared to SD rats. The CA/CDCA ratio in female NA rats was not different from that in their SD counterparts. There were no significant differences between NA and SD rats in the biliary bile flow, bile acid levels in the small and large intestines, fecal bile acid excretion, bile acid concentration in the portal and systemic circulation, and in the pool size of bile acids. The blood lipid concentrations were significantly higher in the NA rats than in the SD rats. The hepatic levels of lipids were not significantly different between the two rat strains. In conclusion, this study showed that metabolism of bile acids in NA rats is not significantly affected, and that the hypercholesterolemia observed in these strains is not related to abnormalities of bile acid metabolism.

Serum α2-macroglobulin and α1-inhibitor 3 concentrations are increased in hypoalbuminemia by post-transcriptional mechanisms

In both the nephrotic syndrome (NS) and hereditary analbuminemia in the Nagase analbuminemic rat (NAR), the plasma protein concentration is nearly normal since albumin is replaced by several high molecular weight proteins. In rats these include the protease inhibitors alpha 2-macroglobulin (alpha 2M), a 720 kDa positive acute phase protein (APP) and alpha 1-inhibitor 3 (alpha 1-I3), a 180 kDa negative APP. There is no known stimulus to increase alpha 1-I3 synthesis, but like albumin and other negative APPs its synthesis decreases during inflammation by transcriptional down-regulation. In hypoalbuminemic states gene transcription of other positive and negative APPs is increased. We report that alpha 2M was increased significantly (12-fold) in NAR and by approximately 50-fold in rats with NS compared to control. The alpha 1-I3 concentration was twice normal in NAR or NS compared to controls, providing approximately half of the total plasma protein. Infusion of human albumin into NAR to raise albumin levels > 20 mg/ml for 24 hours caused a significant decrease in alpha 1-I3 (24.8 +/- 0.6 to 18.7 +/- 0.6 mg/ml, P < 0.0001), equal in magnitude to that caused by 250 micrograms/100 g of endotoxin (23.0 +/- 1.1 to 18.6 +/- 0.6, P < 0.01). The effect of albumin was not an acute phase response since it also suppressed alpha 2M (239 +/- 10 to 205 +/- 11 micrograms/ml, P < 0.005). Turnover of 125I labeled alpha 2M and alpha 1-I3 was then measured in controls, NAR and in two models of the nephrotic syndrome in rats (Heymann nephritis, HN; adriamycin-induced, ADR), yielding fractional catabolic rates (FCR), which at steady state equals synthesis. The serum alpha 2M concentration was increased approximately equal to 50-fold and was proportional to synthesis (r = 0.91 P < 0.001). alpha 2-Macroglobulin synthesis increased by 12-fold in NAR and 50-fold in NS. In contrast, hepatic alpha 2M mRNA increased only 30% in NAR and twofold in NS, suggesting post-transcriptional regulation. Fractional catabolic rates were not decreased and played no role in increasing serum alpha 2M in NS or NAR. The alpha 1-I3 concentration and synthesis increased twofold from controls in both NAR and NS. However, hepatic alpha 1-I3 mRNA was not increased in NAR and increased only 50% in NS. Unlike alpha 2M, serum alpha 1-I3 correlated negatively with FCR (-r = 0.66, P < 0.01). In conclusion, both alpha 1-13 and alpha 2M concentration are increased in hypooncotic states by increased synthesis regulated post-transcriptionally, supporting plasma protein concentration when albumin is lost in urine or not synthesized.

Mechanisms of intrathymic tolerance induction to isolated rat hepatocyte allografts.

Intrathymic injection of alloantigen in young adult rats is capable of mediating long-lived transplantation tolerance. In this study, we use a well-defined model of isolated hepatocyte transplantation to define the mechanisms of intrathymic induced tolerance. The recipient rats are Nagase analbuminemic rats (NAR) that are deficient in albumin, to allow for following transplant acceptance using metabolic and genetic markers. Tolerance to allogeneic hepatocyte transplants could be mediated by intrathymic injection of live allogeneic splenocytes, lethally irradiated splenocytes, or isolated hepatocytes. Intrathymic injection of live allogeneic splenocytes, but not of hepatocytes or irradiated splenocytes, resulted in donor microchimerism in peripheral lymphoid organs, with preferential expansion of CD4-positive T cells in the recipient spleens. Tolerance could be adoptively transferred from tolerant animals to naive recipients, but only from those animals that had been inoculated with intrathymic donor splenocytes. We conclude that donor microchimerism is found after intrathymic inoculation of live splenocytes, but is not required for tolerance induction and that microchimerism is not an absolute requirement for the generation of regulatory cells.

Fetal rat hepatocytes: isolation, characterization, and transplantation in the Nagase analbuminemic rats.

In contrast to adult hepatocytes, fetal hepatocytes (FH) are thought to be highly proliferative, less immunogenic, and resistant to cryopreservation and ischemic injury. These qualities could enhance FH engraftment, proliferation, and gene transfer requiring active DNA synthesis. Rat FH were obtained using the nonperfusion collagenase/DNase digestion method. Free and cultured cells were studied using electron microscopy, fluorescence-activated cell sorting, and Northern analysis using alpha-fetoprotein and albumin as markers of hepatocyte lineage. DNA synthetic activity was measured in quiescent and mitogen-stimulated fetal and adult hepatocytes by [3H]thymidine incorporation. Susceptibility of cultured FH to retrovirally mediated gene transfer was studied using an amphotropic retroviral vector carrying the Escherichia coli lac-Z gene. Nagase analbuminemic rats were used as recipients to study the effects of intraportal FH transplantation. Analysis of serum albumin was carried out by enzyme-linked immunosorbent assay. In fetal liver, 87+/-2% of the cells showed morphological and molecular features of hepatocytes. DNA synthetic activity in nonstimulated cultured FH was 10 times greater than the maximal hepatocyte growth factor-driven response in adult rat hepatocytes. A total of 5-15% FH stained positive for X-gal; results of transduction in adult hepatocyte cultures were negative. In Nagase analbuminemic rat recipients, FH produced significant amounts of albumin only when a hepatic regenerative stimulus was applied. Immunohistochemistry confirmed presence of albumin-positive hepatocytes. Fetal rat liver from the late gestation period is highly enriched with hepatocyte progenitors. They are highly proliferative and susceptible to retroviral transduction and can engraft and function in the adult rat liver if transplanted under a hepatic regenerative stimulus.

Mechanisms of intrathymic tolerance induction to isolated rat hepatocyte allografts

Intrathymic injection of alloantigen in young adult rats is capable of mediating long-lived transplantation tolerance. In this study, we use a well-defined model of isolated hepatocyte transplantation to define the mechanisms of intrathymic induced tolerance. The recipient rats are Nagase analbuminemic rats (NAR) that are deficient in albumin, to allow for following transplant acceptance using metabolic and genetic markers. Tolerance to allogeneic hepatocyte transplants could be mediated by intrathymic injection of live allogeneic splenocytes, lethally irradiated splenocytes, or isolated hepatocytes. Intrathymic injection of live allogeneic splenocytes, but not of hepatocytes or irradiated splenocytes, resulted in donor microchimerism in peripheral lymphoid organs, with preferential expansion of CD4-positive T cells in the recipient spleens. Tolerance could be adoptively transferred from tolerant animals to naive recipients, but only from those animals that had been inoculated with intrathymic donor splenocytes. We conclude that donor microchimerism is found after intrathymic inoculation of live splenocytes, but is not required for tolerance induction and that microchimerism is not an absolute requirement for the generation of regulatory cells. (Hepatology 1997 Nov;26(5):1287-95)

Hypoalbuminemia causes high blood viscosity by increasing red cell lysophosphatidylcholine

Albumin deficiency is accompanied by a reduction in red cell deformability and blood hyperviscosity. Albumin deficiency increases plasma fibrinogen and triglyceride levels and may alter red cell membrane lipid composition. These options, which could all contribute to reduced red cell deformability (RCD) and hyperviscosity, were studied in the Nagase analbuminemic rat (NAR), a mutant Sprague Dawley rat (CON), characterized by normal total protein levels, with an absolute deficiency of albumin, but elevated levels of non-albumin proteins and hyperlipidemia. Plasma protein-binding of the polar phopholipid lysophosphatidylcholine (LPC) was markedly decreased. LPC comprised only 26 +/- 1% of total plasma phospholipids as compared to 42 +/- 2% in CON. NAR red cells in CON plasma had a viscosity that was similar to CON red cells in CON plasma. Conversely, CON red cells in NAR plasma show an increased viscosity as compared to CON red cells in CON plasma. The maximum deformation index of both NAR and CON red cells was markedly decreased in NAR plasma as compared to either NAR or CON cells in CON plasma (0.04 +/- 0.03 and 0.02 +/- 0.02 vs. 0.22 +/- 0.06 and 0.15 +/- 0.04, respectively; P < 0.05). Thus, plasma composition causes hyperviscosity and reduced RCD in NAR. Fibrinogen is not responsible since red cells in serum and red cells in plasma had a similar viscosity and differences in viscosity and RCD between NAR and CON were maintained. Plasma triglycerides are also not responsible since the viscosity of red cells in serum with a 50% reduction in triglycerides was not reduced. LPC levels in red cells were increased in NAR (8.7 +/- 0.2 vs. 5.5 +/- 0.3% of total phospholipids; P < 0.01). Adding albumin to NAR blood dose-dependently decreased whole blood viscosity, despite marked increases in plasma viscosity, and increased RCD of NAR cells (from 0.04 +/- 0.03 to 0.21 +/- 0.01; P < 0.05). There was also some effect on CON RCD of similar albumin addition to CON blood (from 0.15 +/- 0.04 to 0.29 +/- 0.03; P < 0.05). Adding albumin to NAR blood reduced red cell LPC content and increased plasma LPC content in a dose-dependent fashion, whereas there were only slight effects of adding albumin to CON blood. There was a reciprocal relation between red cell LPC and the other polar phospholipids in the red cell membrane, probably indicating exchange. The maximum deformability index of either NAR or CON cells was not affected much by adding LPC to CON plasma (NAR, from 0.22 +/- 0.06 to 0.18 +/- 0.10; CON, from 0.15 +/- 0.04 to 0.12 +/- 0.05; NS), whereas adding LPC to NAR plasma caused the red cells to become rigid. Adding LPC to CON red cells in NAR plasma caused a much stronger increase in relative LPC content (from 6.6 +/- 0.7 to 10.9 +/- 0.9%; P < 0.05) than adding LPC to CON red cells in CON plasma (from 5.6 +/- 0.4 to 6.4 +/- 0.8%; NS). Thus, in the absence of albumin, LPC in red blood cells is increased. As a consequence of the latter, RCD is decreased and whole blood viscosity increased. Alterations in red cell phospholipids are far more important than increases in plasma fibrinogen or triglycerides in determining hyperviscosity of blood and reduced RCD in NAR.

Zinc distribution in the brain of Nagase analbuminemic rat and enlargement of the ventricular system

65ZnCl 2 was intravenously injected into Nagase analbuminemic rats (NAR), which have a genetical mutation affecting albumin mRNA processing and lack serum albumin, to test the hypothesis that albumin is necessary for zinc (Zn) transport into the brain. One hour after injection, 65Zn was largely concentrated in the choroid plexus of NAR as well as normal parental Sprague–Dawley rats (SDR). Six days after injection, in both groups, the 65Zn concentration in the choroid plexus decreased, with increases in other brain regions. The finding that there was no significant difference in brain distribution of 65Zn between NAR and SDR suggests that Zn transport into the brain and its distribution through the blood–cerebrospinal fluid barrier as well as the blood–brain barrier are not dependent on serum albumin. A most interesting observation was that the cerebral ventricles were considerably enlarged in NAR.

Immunoregulation via adhesion molecules in allogenic and xenogenic hepatocyte transplantation to Nagase's analbuminemic rats.

We investigated the effects of monoclonal antibodies (mAbs) against lymphocyte function-associated antigen-1 (LFA-1) and intercellular adhesion molecule-1 (ICAM-1) on intrasplenic allogenic and xenogenic hepatocyte transplantation (HCTx) to analbuminemic rats. Ten to 12-wk-old male Nagase's analbuminemic rats (RT1l) were used as recipients, Wistar/Shi rats (RT1k) were used as donors for allografts and BALB/C mice were used as donors for xenografts. The experimental groups were as follows: group 1, allo-HCTx (n = 7); group 2, allo-HCTx + antirat ICAM-1/antirat LFA-1 mAbs (1.0 mg/kg/day, for 7 days, respectively) (n = 6); group 3, xeno-HCTx (n = 5); group 4, xeno-HCTx + mAbs (antimouse LFA-1/antirat ICAM-1) (n = 5). group 5, xeno-HCTx + mAbs (antirat LFA-1/antimouse ICAM-1) (n = 5). Serum rat albumin levels were measured in groups 1 and 2, and serum mouse albumin levels were measured in groups 3, 4, and 5, as indicators of the function of grafted hepatocytes. In allotransplantation groups, the serum rat albumin levels in the mAbs-treated group were significantly higher than those in the control group for 6 wk after transplantation. In xenotransplantation groups, no increase in the serum mouse albumin levels was detected in any group

Immunoregulation via adhesion molecules in allogenic and xenogenic hepatocyte transplantation to nagase's analbuminemic rats

We investigated the effects of monoclonal antibodies (mAbs) against lymphocyte function-associated antigen-1 (LFA-1) and intercellular adhesion molecule-1 (ICAM-1) on intrasplenic allogenic and xenogenic hepatocyte transplantation (HCTx) to analbuminemic rats. Ten to 12-wk-old male Nagase's analbuminemic rats (RT1 1) were used as recipients, Wistar/Shi rats (RT1 k) were used as donors for allografts and BALB/C mice were used as donors for xenografts. The experimental groups were as follows: group 1, allo-HCTx ( n = 7); group 2, allo-HCTx + antirat ICAM-1/antirat LFA-1 mAbs (1.0 mg/kg/day, for 7 days, respectively) ( n = 6); group 3, xeno-HCTx ( n = 5); group 4, xeno-HCTx + mAbs (antimouse LFA-1/antirat ICAM-1) ( n = 5). group 5, xeno-HCTx + mAbs (antirat LFA-1/antimouse ICAM-1) ( n = 5). Serum rat albumin levels were measured in groups 1 and 2, and serum mouse albumin levels were measured in groups 3, 4, and 5, as indicators of the function of grafted hepatocytes. In allotransplantation groups, the serum rat albumin levels in the mAbs-treated group were significantly higher than those in the control group for 6 wk after transplantation. In xenotransplantation groups, no increase in the serum mouse albumin levels was detected in any group.

Changes in the Albumin Binding of Tryptophan During Postoperative Recovery: A Possible Link With Central Fatigue?

Tryptophan is the precursor of the neurotransmitter 5-hydroxytryptamine (5-HT), known to be involved in sleep and fatigue. In the blood, tryptophan binds to albumin, and that which does not, free tryptophan, competes with branched chain amino acids (BCAA) for entry into the brain. The plasma concentrations of albumin, free tryptophan, total tryptophan, and BCAA were measured before and after major surgery in nine elderly and nine coronary artery bypass graft (CABG) patients. In both the elderly and the CABG patients plasma free tryptophan concentrations were increased after surgery, compared with baseline levels; the plasma free tryptophan/BCAA concentration ratio was also increased significantly after surgery. Plasma albumin concentrations were decreased significantly after surgery in both the elderly and the CABG patients. Plasma BCAA concentrations were not affected by surgery in either group. The effect of exercising to exhaustion on 5-HT and tryptophan were investigated in Nagase analbuminemic rats (NAR). The intrasynaptosomal concentration of tryptophan, 5-hydroxytryptophan, and 5-HT was increased by fatigue after exercise. In addition, running time to exhaustion was shortened in NAR. These data suggest that free tryptophan uptake and 5-HT synthesis were enhanced in the nerve terminal. A decrease in plasma albumin may account for the increase in plasma-free tryptophan levels. An increase in plasma free tryptophan, resulting in an enhanced plasma concentration ratio of free tryptophan/BCAA, may lead to a higher 5-HT concentration in some parts of the brain and, consequently, to central fatigue. It is suggested that provision of BCAA as a dietary supplement may counteract the increase in plasma free tryptophan and thus improve the status of some patients after major surgery.

Toxicity of amphotericin B to analbuminemic rats

Nagase analbuminemic rats (NAR), a strain derived from Sprague Dawley rats (SDR), are suitable to determine the in vivo effect of hyperlipidemia and analbuminemia on the toxicity of the antifungal agent amphotericin B (AB). Cholesterol content was increased in all plasma lipoprotein fractions when SDR serum was compared with NAR serum. Incubation of AB with plasma from animals of both strains and further isolation of plasma lipoprotein by ultracentrifugation, showed that, while in SDR approximately 40% of the injected AB was in the lipoprotein fraction, in NAR almost all (approximately 80%) AB was associated with lipoproteins, especially in the low density lipoprotein fraction. AB spectrophotometry showed differences in the extent of AB aggregation between SDR and NAR plasma fractions. The lack of albumin results in aggregation of the AB present in the infranatant fraction. In vivo, a strong reduction in lethality was observed for NAR when compared to SDR (LD 50% of 6.4 and 1.9 mg/kg respectively). The preferential distribution of AB in the plasma lipoprotein fraction seems to affect pharmacological parameters, with a consequent reduction of toxicity.

Long-term correction of albumin levels in the nagase analbuminemic rat: Repopulation of the liver by transplanted normal hepatocytes under a regeneration response

Numerous studies have reported successful transplantation of hepatocytes with demonstration of function. However, none have shown long-term correction of a liver-related metabolic defect. Male Nagase analbuminemic rats, immunosuppressed with cyclosporin-A, were transplanted with normal hepatocytes (2 × 10 7 cells/rat) isolated from allogeneic male Sprague-Dawley rat donors. Hepatocytes were selectively transplanted via the portal vein tributary into the posterior liver lobes of Nagase analbuminemic rats. Following 2 wk, to allow engraftment, selected transplanted rats (Group I) were reoperated and the portal venous branch supplying the anterior liver lobes was permanently ligated, resulting in their atrophy and induction of regeneration in the residual transplant-bearing lobes. Control rats consisted of: Group II—transplanted with normal hepatocytes without portal branch ligation; Group III—transplanted with analbuminemic hepatocytes with portal branch ligation; and Group IV-nontransplantedanalbuminemic rats with portal branch ligation. The experimental period extended to 3 mo posttransplantation. All rats transplanted with normal hepatocytes demonstrated a significant elevation in serum albumin levels (ELISA). Group I rats had dramatic elevations in serum albumin to near normal levels (1.78 ±0.20 g/dl), and maintained these levels until the end of the experiment. Albumin levels in Group II rats reached 0.26 ±0.07 g/d1( p < 0.001), whereas Group III and IV rats showed no changes in serum albumin levels throughout the experiment. Immunohistology of liver tissue obtained from Group I rats, demonstrated large numbers (22.6 ±7.5%) of albumin-positive hepatocytes populating the recipient liver. This is the first report of near-total and sustained correction of a genetic defect in liver function in an experimental animal model following allogeneic hepatocyte transplantation.

Ovariectomy decreases plasma triglyceride levels and both prevents and alleviates glomerular disease in uninephrectomized female analbuminemic rats.

Female Nagase analbuminemic rats (NAR) are profoundly hypertriglyceridemic and develop proteinuria and glomerulosclerosis when aging and after uninephrectomy (UNX). Ovariectomy (OVX) markedly decreases plasma triglyceride levels in this species. This study evaluated whether decreasing triglyceride levels by OVX could prevent renal disease or alleviate its progression in UNX female NAR. Female NAR underwent OVX at 0, 12, 24, or 36 wk after UNX. In the absence of OVX, the animals developed progressive proteinuria from 18 wk after UNX and showed extensive glomerular sclerosis, lipid deposition, and hypertrophy at euthanasia (49 wk after UNX). These changes were prevented by OVX carried out at 0 or 12 wk, and attenuated by OVX at 24 wk after UNX. If performed at 36 wk after UNX, OVX had no effect on glomerulosclerosis, although it reduced proteinuria. In 95% (20 of 21) of the rats with proteinuria over 10 mg/day, proteinuria decreased in the first 6 wk after OVX. The percentage decrease in proteinuria correlated inversely with the glomerulosclerosis score at euthanasia (r = -0.58, P < 0.01). OVX had no effect on hyperfiltration and hyperperfusion in the UNX rats. OVX consistently reduced plasma triglyceride levels in rats both with and without proteinuria, and it also reduced plasma cholesterol, but only in conjunction with reduction in proteinuria. It was concluded that OVX in UNX female NAR prevents glomerulosclerosis if performed before proteinuria and attenuates further development of established renal disease if performed in a timely manner. This study's data suggest that in UNX female NAR, the lowering of plasma triglyceride levels plays a central role in the renoprotective action of OVX.