Rat Pancreatic Tissue Research Articles

New kids on the block: pancreatic stellate cells enter the fibrogenesis world

See article on page 534 Two recently published papers have shown that a cell type with morphological features of “vitamin A storing” stellate cells is present in rat and human...

Major histocompatibility complex class II expression and parathyroid autoantibodies in primary hyperparathyroidism

Background: Autoimmune diseases are characterized by induced parenchymal expression of major histocompatibility complex (MHC) class II antigens and circulating autoantibodies directed toward surface structures on the target cells. MHC class II expression can be modified by viral infections of potential pathogenic importance in autoimmune reactions. Primary hyperparathyroidism exhibits an incompletely clarified cause. Methods: With cryosections, human parathyroid glands were stained with monoclonal antibodies to MHC class II antigens according to a peroxidase-antiperoxidase technique. Human parathyroid adenoma tissue transplanted to nude mice and rat parathyroid glands was tested with serum from patients with hyperparathyroidism and control subjects. Results: Induced MHC class II expression was demonstrated on parathyroid parenchymal cells in 13 of 54 adenomatous and eight of 23 hyperplastic glands of patients with primary hyperparathyroidism. This reactivity was absent in 12 normal glands, nine normal-sized glands associated with the adenomas, and 17 enlarged glands of patients with hyperparathyroidism caused by uremia. Staining of parathyroid tissue was found with serum from 27 of 38 patients with primary hyperparathyroidism, whereas this reactivity was absent on rat thyroid and pancreatic tissue, as well as with control sera. Conclusions: The concurrent induction of MHC class II antigen expression and circulating antiparathyroid autoantibodies in 16 of 38 patients with primary hyperparathyroidism suggests hitherto unrecognized immunologic involvement in this disease. (Surgery 1998;124:503-9.)

Major histocompatibility complex class II expression and parathyroid autoantibodies in primary hyperparathyroidism

Background: Autoimmune diseases are characterized by induced parenchymal expression of major histocompatibility complex (MHC) class II antigens and circulating autoantibodies directed toward surface structures on the target cells. MHC class II expression can be modified by viral infections of potential pathogenic importance in autoimmune reactions. Primary hyperparathyroidism exhibits an incompletely clarified cause. Methods: With cryosections, human parathyroid glands were stained with monoclonal antibodies to MHC class II antigens according to a peroxidase-antiperoxidase technique. Human parathyroid adenoma tissue transplanted to nude mice and rat parathyroid glands was tested with serum from patients with hyperparathyroidism and control subjects. Results: Induced MHC class II expression was demonstrated on parathyroid parenchymal cells in 13 of 54 adenomatous and eight of 23 hyperplastic glands of patients with primary hyperparathyroidism. This reactivity was absent in 12 normal glands, nine normal-sized glands associated with the adenomas, and 17 enlarged glands of patients with hyperparathyroidism caused by uremia. Staining of parathyroid tissue was found with serum from 27 of 38 patients with primary hyperparathyroidism, whereas this reactivity was absent on rat thyroid and pancreatic tissue, as well as with control sera. Conclusions: The concurrent induction of MHC class II antigen expression and circulating antiparathyroid autoantibodies in 16 of 38 patients with primary hyperparathyroidism suggests hitherto unrecognized immunologic involvement in this disease. (Surgery 1998;124:503-9.)

Protein Kinase B Is Expressed in Pancreatic β Cells and Activated upon Stimulation with Insulin-like Growth Factor I

Protein kinase B (PKB) is involved in signaling to a multitude of important cellular events and is activated by insulin and growth factors, including insulin-like growth factor I (IGF-I). We show here expression of PKB in pancreatic islets and in the β cell lines HIT-T15, INS-1, and RINm5F. Expression of PKB mRNA and the presence of PKB isoforms (α, β, and γ) were assessed by Northern blot analysis and RT-PCR, respectively. Antibodies recognizing different parts of PKB isoforms were employed to demonstrate PKB protein expression by immunoblot analysis. By use of immunohistochemistry in rat and mouse pancreatic tissue sections, PKB was localized to predominantly β cells. Regulation of PKB was examined in INS-1 and RINm5F cells; upon stimulation with IGF-I (5–10 min), PKB was phosphorylated and activated (≈3-fold) by a wortmannin-sensitive mechanism, indicating involvement of phosphatidylinositol-3 kinase. The possible participation of PKB in signal transduction pathways modulating cAMP-dependent insulin secretion and in proliferation of β cells is discussed.

Expression of NHE1 and NHE4 in Rat Pancreatic Zymogen Granule Membranes

We previously characterized a Na+/H+exchange activity in rat pancreatic zymogen granules [Anderie, I., and Thévenod, F. (1996)J. Membrane Biol.152, 195-205]. Here we have identified the Na+/H+exchanger (NHE) isoforms present in zymogen granules by functional studies with NHE inhibitors. The NHE1 specific blocker HOE 694 [3-(methylsulfonyl-4-piperidino-benzoyl)-guanidine methanesulfonate] inhibited zymogen granule Na+/H+exchange in a concentration dependent manner, maximally to 53 ± 5% of controls at 100nM. The remaining Na+/H+exchange activity was inhibitable by EIPA [5-(N-ethyl-N-isopropyl)amiloride] (EC50∼ 25μM) or benzamil (EC50∼ 100μM). Amiloride inhibited weakly suggesting that “amiloride-resistant” and “amiloride-sensitive” NHE are expressed in zymogen granules. cDNA sequences encoding NHE1- and NHE4-specific transmembrane domains were detected by RT-PCR in rat pancreatic tissue and in the rat pancreatic acinar cell line AR4-2J. The presence of NHE1 and NHE4 in zymogen granule membranes was confirmed by immunoblots of zymogen granule membranes and by pre-embedding immunogold labeling of purified rat pancreatic zymogen granules with polyclonal NHE1 and NHE4 antibodies. Therefore, we propose that NHE1 and NHE4 are expressed in zymogen granule membranes of rat exocrine pancreas.

Pancreatic DNA adducts formed in vitro and in vivo by the food mutagens 2-amino-1-methyl-6-phenylimidazo[4,5- b]pyridine (PhIP) and 2-amino-3-methyl-9 H-pyrido[2,3- b]indole (MeAαC)

Genotoxic heterocyclic amines have been detected in grilled or fried meat and tobacco smoke. Among these, 2-amino-1-methyl-6-phenylimidazo[4,5- b]pyridine (PhIP) and 2-amino-3-methyl-9 H-pyrido[2,3- b]indole (MeAαC) have been shown to induce tumours in rodents in several organs. Here we report on the DNA adduct formation by PhIP and MeAαC in vitro and in vivo, both in rat hepatic and rat pancreatic tissues or cells. Using 32P-postlabelling analysis both compounds were shown to induce a dose-dependent DNA modification in primary rat hepatocytes that was correlated with cytotoxicity in these cells. In explanted rat pancreas maintained in dynamic short-term organ culture MeAαC was shown to induce covalent DNA adducts. No DNA adducts were observed with PhIP in this assay. DNA adducts were observed in the liver and the pancreas of F344 rats treated with PhIP, with a 36-times higher level of adducts in the pancreas, confirming data reported earlier. DNA adduct levels induced by feeding 32, 160 or 800 ppm MeAαC in the diet were dose-dependent and higher in the liver compared with other organs including pancreas. While for PhIP the N 2-(desoxyguanin-8-yl)-derivative was accounting for more than 90% of DNA adducts detected, in the case of MeAαC the N 2-(desoxyguanin-8-yl) adduct was predominant in vitro and determined in vivo as one of up to 5 DNA adducts. MeAαC had been reported to induce preneoplastic foci and tumours in the liver and tumours and atrophy in the pancreas. In the case of MeAαC, the DNA adduct formation and cytotoxicity observed by us in vitro and in vivo correlate with the organ specificity of the reported pathological lesions. In the case of PhIP our in vitro data in pancreas and liver and the low adduct levels in liver in vivo also reflect the reported lack of pathological effects in these organs. In contrast, in pancreas, in vivo extraordinarily high adduct levels induced by PhIP were observed confirming studies published earlier, in spite of the fact that this compound does not cause pancreatic lesions. This enigmatic observation is discussed and the relevant literature is reviewed.

Predominant Expression of an Arachidonate Epoxygenase in Islets of Langerhans Cells in Human and Rat Pancreas

Our laboratory recently described a new human cytochrome P450 arachidonic acid epoxygenase (CYP2J2) and the corresponding rat homolog (CYP2J3). Immunoblotting studies using a polyclonal antibody raised against recombinant human CYP2J2 confirmed CYP2J protein expression in human and rat pancreatic tissues. Immunohistochemical staining of formalin-fixed paraffin-embedded rat and human pancreas using the anti-CYP2J2 IgG and avidin-biotin-peroxidase detection revealed that CYP2J2 protein expression was highly localized to cells in the islets of Langerhans, with minimal staining in pancreatic exocrine cells. Colocalization studies using antibodies to the glucagon, insulin, somatostatin, and pancreatic polypeptide as markers for alpha-, beta-, delta-, and PP cells, respectively, showed that CYP2J protein expression was abundantly present in all four cell types, but was highest in the glucagon-producing alpha-cells. Direct evidence for the epoxidation of arachidonic acid by pancreatic cytochrome P450 was provided by documenting, for the first time, the presence of epoxyeicosatrienoic acids in vivo in human and rat pancreas by gas chromatography/mass spectrometry. Importantly, the levels of immunoreactive CYP2J2 in different human pancreatic tissues were highly correlated with endogenous epoxyeicosatrienoic acid concentrations. We conclude that human and rat pancreas contain an arachidonic acid epoxygenase belonging to the CYP2J subfamily that is highly localized to islet cells. These data together with previous work showing effects of epoxyeicosatrienoic acids in stimulating insulin and glucagon secretion from isolated rat pancreatic islets support the hypothesis that epoxygenase products may be involved in stimulus-secretion coupling in the pancreas.

Tissue Homogenization as a Key Step in Extracting RNA from Human and Rat Pancreatic Tissue

Tissue Homogenization as a Key Step in Extracting RNA from Human and Rat Pancreatic Tissue

Members of the MAZ Family: A Novel cDNA Clone for MAZ from Human Pancreatic Islet Cells

A human recombinant cDNA clone that encoded a zinc-finger protein (Myc-associatedzinc-finger protein of humanislet; MAZi) was cloned by screening a cDNA library prepared from human pancreatic islet cells. The encoded protein showed a high degree of homology to theMyc-associated zinc-finger protein MAZ (ZF87 or Pur-1). However, differences between the cDNAs for MAZi and MAZ were found in the length of the encoded polyalanine stretch and in the sequence of the 5′-end leader. MAZi transcripts were significantly more abundant in rat pancreatic islet carcinoma tissue than in normal rat islet cells. Moreover, MAZi protein bound specifically to the pyrimidine-rich strand of the CT-element of thec-mycgenein vitroand strongly induced the expression of chloramphenicol acetyltransferase (CAT) from ac-mycpromoter/CAT reporter construct in human pancreatic cells. Our results suggest that a distinct member of the MAZ family is expressed in human islet cells and enhances the transcriptional activity of thec-mycgene.

In vivo documentation of an arteriovenous shunt in rat pancreatic acinar tissue.

With the use of epiilumination fluorescence microscopy, we demonstrate for the first time in vivo the existence and function of direct arteriovenous communication (arteriovenous shunt) in rat pancreatic acinar tissue. In eight Sprague-Dawley rats the corpus and tail of the pancreatic gland were reviewed for arteriovenous anastomoses. In seven animals the technique did not allow us to visualize completely the arteriolar and venular vascular system due to overlying pancreatic tissue. In one animal, however, the vascular trees could be identified in their continuity over a length of several millimeters, including an arteriovenous shunt with a diameter of 12.0 microns. Analysis of volumetric blood flow revealed that 86.2% (15.61 nl/min) of the arteriolar blood volume was shunted into the venule, while only 13.8% (2.50 nl/min) of the blood volume was carried by the arteriole distal to the arteriovenous shunt to the nutritive capillary bed. There were no changes in diameter, i.e., vasoconstriction, vasodilation, or vasomotion, over an observation period of 30 min, indicating that, at least under physiological conditions, this arteriovenous communication functioned as a real "fare-through" channel.

Vasoactive intestinal peptide (VIP)-induced enzyme secretion in rat pancreatic tissue is not associated with activation of nitric oxide synthase (NOS) and increase in cyclic GMP level

Nitric oxide (NO) is thought to be a second messenger involved in secretion. Upon stimulating pancreatic acinar cells with cholecystokinin- pancreozymin (CCK-PZ), NO formation has been shown to be associated with increased levels of cGMP (Seoet al., 1995). To elucidate the signaling pathway of VIP-induced enzyme secretion, we investigated the NO and cGMP synthesis steps as potential steps where two signal pathways triggered by CCK-PZ and VIP interact. The results obtained in this work provide evidence that increase in pancreatic enzyme secretion by treatment with VIP has no relationship with NOS activity and cGMP level. This conclusion was derived from the following findings that VIP treatment of rat pancreatic tissue increased amylase release as well as protein output in a dose- and time-dependent manner, whereas NOS activity and cGMP synthesis were not affected by VIP treatment as monitored by NOS activity assay and determining cGMP level, which was further confirmed by a NOS-inhibitor study. Consequently, CCK-PZ or VIP increases enzyme secretion in rat pancreatic tissue, but the two hormones are different in their mode of action. Together the results suggest that signaling pathway of VIP-induced enzyme secretion might either bypass the NO and cGMP synthesis steps or lie on a distinct pathway from CCK-PZ-induced pathway.

Gastrin Receptor Expression during Azaserine-Induced Rat Pancreatic Carcinogenesis

The hormone gastrin is thought to stimulate the growth of certain pancreatic carcinoma cell lines. We have previously detected the presence of the gastrin receptor in rat pancreatic carcinoma cell lines but not in normal rat pancreas. We had not, however, previously demonstrated that gastrin receptor is expressed in pancreatic carcinomas developing in the ratin vivo.Therefore, in the present study, we examined rat pancreatic tissue at various stages in azaserine-induced pancreatic carcinogenesis for gastrin binding and for the presence of gastrin receptor mRNA to determine the temporal expression pattern of the gastrin receptor during thein vivodevelopment of pancreatic cancer. Autoradiography of pancreatic tissue using125I-gastrin-17-I from all azaserine-treated and control animals at 2, 4, 8, and 12 months of age demonstrated no specific gastrin binding. At 18 months of age, normal pancreas, azaserine-induced premalignant pancreatic nodules, and internodular pancreas demonstrated no specific gastrin binding. One of three azaserine-treated animals developed an area of pancreatic acinar cell carcinoma at 18 months of age which exhibited significant specific gastrin binding of 141.8 ± 32.8 fmole/gm of tissue. Southern blot analysis of pancreatic RNA isolated from animals at 12 months of age revealed no gastrin receptor mRNA; however, by 18 months of age, gastrin receptor mRNA was present in all azaserine-treated animals but absent in control animals. In summary, specific gastrin binding is present inin vivoazaserine-induced pancreatic acinar cell carcinoma but absent in normal pancreas and azaserine-induced premalignant pancreatic nodules. Gastrin receptor mRNA is first expressed in azaserine-treated rat pancreas at some point between 12 and 18 months of age. These results demonstrate that expression of gastrin receptor is altered in azaserine-treated rat pancreas and may play a role in the development of pancreatic cancer.

Acute ethanol administration induces oxidative changes in rat pancreatic tissue.

There is mounting clinical evidence that ethanol toxicity to the pancreas is linked with glutathione depletion from oxidative stress but there is not experimental proof that this occurs. The effect of acute ethanol ingestion (4 g/kg) on the pancreatic content of reduced (GSH) and oxidised (GSSG) glutathione, malondialdehyde (MDA), and carbonyl proteins were therefore studied in the rat. Ethanol caused a significant reduction in GSH (p < 0.02) and an increase in GSSG (p < 0.005), MDA (p < 0.05), and carbonyl proteins (p < 0.05) in the rat pancreas. The GSH/GSSG ratios were significantly decreased after ethanol, especially in rats pretreated with diethylmaleate (DEM), a GSH blocker. Administration of ethanol after DEM further increased the rate of lipid and protein oxidation. Pretreatment with cyanamide (an inhibitor of aldehyde dehydrogenase) but not with 4-methylpyrazole (an alcohol dehydrogenase inhibitor) caused higher production of GSSG and MDA. These findings indicate that acute ethanol reduces the pancreatic content of GSH, which seems to be protective against ethanol toxicity, since its depletion is accompanied by increased oxidative damage to cell structures. The further increase of lipid peroxidation and GSSG production in the presence of cyanamide suggests that acetaldehyde might be responsible for the oxidative changes that occur in pancreatic cells after ethanol administration.

Small-volume resuscitation restores hemorrhage-induced microcirculatory disorders in rat pancreas.

Pancreatic hypoxia/ischemia, as a consequence of shock-induced microcirculatory failure, is considered a causative factor in the initiation and/or progression of pancreatic tissue injury. The aim of this study was to compare the effects of "small volume resuscitation" with conventional isovolemic colloid and hypervolemic crystalloid resuscitation on pancreatic microcirculation after hemorrhagic shock. Randomized, controlled intervention trial. University laboratory. Twenty-three male Sprague-Dawley rats anesthetized with á-chloralose mechanically and ventilated. Rats subjected to 1 hr of hemorrhagic shock (mean arterial pressure of 40 mm Hg) were resuscitated with lactated Ringer's solution (four-fold shed volume/20 mins), 10% hydroxyethyl starch (shed volume/5 mins), or 7.2% sodium chloride-10% hydroxyethyl starch (10% shed volume/2 mins). The microcirculation of pancreatic acinar tissue was studied by means of intravital fluorescence microscopy and laser Doppler flowmetry. At 1 hr after resuscitation, mean arterial pressure, pancreatic capillary erythrocyte velocity, and erythrocyte flux were found to be significantly increased when compared with those values in the shock state. However, mean arterial pressure, pancreatic capillary erythrocyte velocity, and erythrocyte flux did not completely return to preshock values, regardless of the type of fluid used for resuscitation. At 15 mins and 1 hr after resuscitation, shock-induced capillary perfusion failure (reduction of functional capillary density) was restored to 91% to 94% of baseline values in all groups. Pancreatic capillary narrowing, indicating microvascular endothelial cell swelling, was abolished by resuscitation with both isotonic hydroxyethyl starch and hypertonic hydroxyethyl starch (p<.05 vs. lactated Ringer's solution). Despite replacement of only 10% of actual blood loss, small-volume resuscitation with hypertonic hydroxyethyl starch is as effective as the ten-fold volume of isotonic hydroxyethyl starch and, due to prevention of microvascular endothelial cell swelling, superior to the 40-fold volume of isotonic lactated Ringer's solution in regard to restoration of the shock-induced microcirculatory disturbances of rat pancreatic acinar tissue.

Functional Relationship between a 65-kD mdr1 P-Glycoprotein and ATP-Activated Chloride Conductance in Pancreatic Zymogen Granule Membranes

Zymogen granule (ZG) membranes contain a regulated Cl– conductance which may contribute to secretagogue-induced enzyme, salt and fluid secretion. ATP and nonhydrolyzable ATP analogs, such as adenosine 5’-[βγ-methylene]triphosphate (AMP-PCP) increase ZG membrane (ZGM) Cl– conductance. Here we demonstrate that monoclonal antibodies (mAbs) against multidrug resistance (MDR1) P-glycoprotein inhibit AMP-PCP-activated rat ZG Ch conductance. Moreover, in ZG from mdrla knockout mice, AMP-PCP-activated Cl– conductance is reduced by about 50%. Immunocytochemistry of rat pancreatic tissue using mAbs against MDR1 reveals labeling of the surface of acinar ZG and of apical membranes of pancreatic ducts. A ∼ 180-kD protein is detected in pancreatic duct cell lysates, as expected for full-length P-glycoprotein, and a ∼ 65-kD protein is labeled in ZGM. A high-affinity probe for dihydropyridine-binding domains on MDR1, a benzoyldihydrocinnamic acid derivative of dihydropyridine ((-)-[3H]BZDC-DHP), binds to ZGM with high affinity (Kd ∼ 8 nM), which resembles the binding affinity of full-length MDR1 P-glycoprotein. However, the profile of pharmacological modulation of (-)-[3H]BZDC-DHP binding differs from that of full-length MDR1. The data suggest that ZGM express a marl gene product distinct from the known mdr1 proteins, that may be functionally associated with AMP-PCP-activated ZG Cl- conductance.

Effect of cholecystokinin-pancreozymin on the nitric oxide synthase activity and cyclic GMP level in rat pancreatic tissue

In pancreatic cells, NO formation is associated with increased levels of cGMP and endocrine/ exocrine secretion. In the present study, the role of NO in the regulation of exocrine secretion was investigated in rat pancreatic tissues. Treatment of rat pancreatic tissue with cholecystokinin-pancreozymin (CCK-PZ) resulted in an significant increase in arginine conversion to citrulline, the amount of nitrite/nitrate, the release of amylase, and the level of cGMP. Furthermore, CCK-PZ-stimulated increase of amylase release and conversion of arginine to citrulline transformation were counteracted by the inhibitor of NO synthase, NG-nitro-L-arginine methyl ester. The results on the time course of CCK-PZ-induced citrulline formation and rise of cGMP level indicate that NO synthase and guanylate cyclase are activated within the first seconds of stimulation. The kinetics of citrulline accumulation correlate well with those of cGMP rise, which further confirms the conclusion that NO mediates the response to CCK-PZ by cGMP.

Possibilities of false immunocytochemical results generated by the use of monoclonal antibodies: the example of the anti-proinsulin antibody.

The immunocytochemical application of a monoclonal antibody (MAb) against the Arg-Arg region at the junction of the C-peptide and the insulin beta-chain of the human proinsulin molecule on rat pancreatic tissue resulted in positive immunogold labeling over the insulin- as well as the glucagon-secreting cells. In the insulin cells, the Golgi cisternae and the immature clathrin-coated granules were intensely labeled, and in the glucagon cells all the granules were labeled. Control experiments using the anti-proinsulin MAb adsorbed with proinsulin, insulin, and glucagon have confirmed the crossreactivity of this proinsulin antibody with glucagon. Furthermore, the anti-proinsulin MAb appears to crossreact not only with rat but also with human glucagon and with bovine and porcine insulin and glucagon. Examination of the amino acid sequences of proinsulin and proglucagon has shown that both molecules display this Arg-Arg dipeptide sequence, which could explain the labeling obtained on both cell types. In addition, other propeptides also display such a sequence and, indeed, positive cells were detected in rat pituitary. These results demonstrate that by immunocytochemistry this MAb, although providing very specific results, reveals non-related molecules. This is due to the fact that these molecules exhibit similar short determinants. MAbs raised against very short amino acid sequences can reveal this determinant in various molecules, generating false-positive results.

Presence in human eosinophils of a lysophospholipase similar to that found in the pancreas.

The supernatant fraction from lysed human eosinophils, when separated by gel-filtration chromatography, contains a protein with lysophospholipase activity of approximate molecular mass 74 kDa. This mass differs substantially from the 17 kDa of a previously cloned eosinophil lysophospholipase (Charcot-Leyden crystal protein), but is similar to that reported for a pancreatic enzyme. We have therefore further characterized this pancreatic-like lysophospholipase in human eosinophils. A rabbit polyclonal antibody was produced against a synthetic peptide consisting of amino acids 325-349 from the 74 kDa rat pancreatic lysophospholipase. Western-blot analysis of eosinophil extracts indicate that this antibody recognizes a single 74 kDa band in these preparations. Incubation of the supernatant fraction from sonified eosinophils with this antibody, followed by precipitation of antibody-antigen complexes with Protein A, removes the majority of the lysophospholipase activity. Indirect immunofluorescence examination with this antibody indicates this protein to be localized to granules of eosinophils and not in other leucocytes. Moreover, reverse transcriptase PCR of polyadenylated RNA from eosinophils and from rat pancreatic tissue with primers to rat pancreatic lysophospholipase resulted in readily detectable 1 kb DNA products in both samples. Sequencing revealed this DNA fragment to be identical with the human pancreatic lysophospholipase cDNA sequence. Taken together, these data indicate that eosinophils contain a lysophospholipase that is similar to the human pancreatic enzyme.

Evidence for the role of pancreatic acinar cells in the production of ornithine and guanidinoacetic acid by L-arginine:glycine amidinotransferase.

L-Arginine:glycine amidinotransferase (transamidinase) occurs at high concentrations in the kidney and the pancreas of rats. The cellular localization of transamidinase was investigated in fetal, neonatal, and adult rat pancreatic tissue using three indicators of the presence of transamidinase: (1) immunofluorescence microscopy, (2) in vitro enzymatic activity measurements on homogenates of whole pancreas and on isolated acinar and islet tissue from adult rats, and (3) ornithine production from perfused adult rat pancreas. The cellular localization of transamidinase was determined in fetal, neonatal, and adult rat pancreas, using a polyclonal guinea pig antibody made against a highly purified preparation of kidney transamidinase. Immunoreactive transamidinase was detected only in the pancreatic acinar cells. The cellular distribution of the immunostaining was compatible with the presence of transamidinase in mitochondria. The transamidinase enzymatic activity of whole pancreatic homogenates was 13.4 +/- 0.7 U/g wet weight (n = 11). In pancreata where islets had been isolated away from the acinar tissue, the transamidinase activity was similar to that of the whole pancreatic homogenates (16.8 +/- 2 U/g wet weight). Any transamidinase activity present in isolated islets was below the sensitivity of the assay. Transamidinase activity in the isolated perfused pancreas was determined by measuring the amount of ornithine released into the perfusate. The transamidinase activity of the perfused pancreas was 16.4 +/- 1.8 U/g pancreas and is an estimate of the physiological production capacity of the enzyme (270 +/- 29 nmol ornithine/min/g pancreas). These results indicate that transamidinase is present at high concentrations in the pancreas.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemorrhagic hypotension induces arteriolar vasomotion and intermittent capillary perfusion in rat pancreas.

Hemorrhage-induced intermittent capillary perfusion and its relation to arteriolar vasomotion was studied in rat pancreatic acinar tissue using intravital fluorescence microscopy. During prehemorrhage conditions, microscopic analysis of the pancreatic microcirculation displayed neither arteriolar vasomotion nor intermittency of capillary perfusion (n = 22 animals). Hemorrhage-induced hypotension of 40 mmHg provoked arteriolar vasomotion in 18 of 22 animals and 59 of 115 arterioles studied. The maximum relative amplitude of arteriolar vasomotion was 44 +/- 8% (range 12-81%), and vasomotion frequency averaged 4.73 +/- 0.11 cycles/min. Hemorrhagic hypotension was further accompanied by 1) a decrease of functional capillary density [length of red blood cell-perfused capillaries per area of tissue under investigation (cm/cm2)] from 515 +/- 3 cm-1 at baseline to 386 +/- 3 cm-1 (P < 0.05) and 2) the instantaneous occurrence of intermittency of capillary perfusion in all observation areas (N = 220) of the 22 animals studied. The frequency of intermittency of capillary perfusion (4.72 +/- 0.14 cycles/min) did not differ from the frequency of arteriolar vasomotion, which implies a causal relationship between these two hemorrhage-induced microvascular mechanisms with the probable aim to counteract the decrease of functional capillary density.