Age-matched Normal Rats Research Articles

Ovarian Carbonyl Reductase Delayed Onset of Persistent Estrus in the Offspring of Parathyroidectomized Mother Rats

We investigated the effects of maternal parathyroidectomy on day 5 of pregnancy on the ovarian carbonyl reductase (CR) in the offspring of rats. Changes in the ovarian CR of the offspring were examined at 4 and 8 months of age. In 8-month-old female offspring, the ovarian weight and the ovarian CR activity were significantly higher in rats from parathyroidectomized mothers than in rats from sham-operated mothers, and the offspring of the parathyroidectomized mothers showed the regular 4-day estrous cycles at 8 months of age, while the offspring of the sham-operated mothers were in the state of persistent estrus. Furthermore, intense immunostaining was found in the theca interna cells and the interstitial gland cells in the ovary of rats from the parathyroidectomized mothers, whereas in the ovary of the age-matched normal rats, immunostaining was faint. These results suggest that the maternal parathyroidectomy affect the activity and localization of CR in the ovary of female offspring.

Diminished transient outward currents in rat hypertrophied ventricular myocytes.

Action potential duration is prolonged in ventricular hypertrophy induced by sustained pressure overload. Since the transient outward current (I(to)) is a major factor for determining action potential duration in rat ventricular cells, we used patch-clamp techniques to compare the characteristics of I(to) in normal and hypertrophied left ventricular cells of the rat. Left ventricular pressure overload was induced by partial ligation of the abdominal aorta for 4 to 6 weeks before study. Age-matched normal rats served as controls. Pressure overload increased the heart weight-to-body weight ratio by 47.7%. I(to) was significantly smaller in hypertrophied cells than in normal cells (20.0 +/- 1.3 versus 31.0 +/- 2.1 pA/pF, respectively, at a test potential of +60 mV; P < .001). There were no differences in the steady-state inactivation, the inactivation time course, and the time course of recovery from inactivation between normal and hypertrophied cells. At the single-channel level, there were no differences in the unitary current amplitude of the single I(to) channel between normal and hypertrophied cells, and the slope conductance was 13.7 picosiemens in normal cells and 13.4 picosiemens in hypertrophied cells. The maximum open-state probability, which was estimated from the ratio of the peak of the ensemble-averaged currents to the single-channel current amplitude, was similar for normal and hypertrophied cells (0.66 +/- 0.03 and 0.69 +/- 0.04, respectively, at a test potential of +40 mV; P = NS). We conclude that diminished I(to) contributes to action potential prolongation in hypertrophied ventricular cells from pressure-overloaded rat hearts. Reduced I(to) channel density may be responsible for the diminished whole-cell I(to).

Diminished effect of cAMP on Ca2+ accumulation in skinned fibers of hypertrophied rat heart

Sarcoplasmic reticulum (SR) Ca2+ uptake is reduced in the hypertrophied ventricle. To determine whether events initiated by beta-adrenergic stimulation are involved, we compared the effects of adenosine 3',5'-cyclic monophosphate (cAMP) on SR Ca2+ uptake between normal and pressure-overloaded hypertrophied hearts using saponin-skinned rat left ventricular muscles. Left ventricular pressure overload was induced by partial ligation of the abdominal aorta for 4-6 wk before study. Age-matched normal rats served as controls. Pressure overload increased the left ventricular weight-to-body weight ratio 60.8%. The SR was loaded by exposing the muscles to 10(-6) M Ca2+ solution; SR Ca2+ release was induced by 5 or 25 mM caffeine, and the amount of Ca2+ released from the SR was estimated by the area under the caffeine-induced transient contraction. Concomitant exposure to 10(-4) M cAMP did not influence caffeine-induced Ca2+ release in either normal or hypertrophied fibers. When 10(-4) M cAMP was applied during the Ca(2+)-loading periods, the amount of Ca2+ accumulated by the SR increased in both normal and hypertrophied fibers. However, the extent of increase was significantly smaller in hypertrophied fibers than in normal fibers [10.9 +/- 1.7 and 27.4 +/- 5.3% in 1 min of Ca2+ loading (P < 0.05), 12.2 +/- 3.2 and 24.7 +/- 3.8% in 4 min of Ca2+ loading (P < 0.05), respectively]. cAMP (10(-4) M) shifted the force-pCa relationship to the right similarly in normal and hypertrophied muscles, and there was no difference in the force-pCa relationship between the two groups either with or without cAMP.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanisms of hyperkalemia associated with hyporeninemic hypoaldosteronism in streptozotocin-induced diabetic rats.

This study was aimed at investigating the mechanisms of clinically important overt hyperkalemia in diabetes mellitus with underlying hyporeninemic hypoaldosteronism known as a classic model of the syndrome of hyporeninemic hypoaldosteronism (SHH). Rats (Sprague-Dawley, male) were streptozotocin-treated (60 mg/kg, ip) and used after 60 days. Rats with plasma glucose levels higher than 300 mg/dL (mean +/- SEM, 423 +/- 20 mg/dL, n = 8) were selected as the diabetic group. Age-matched normal rats served as control (mean plasma glucose, 88 +/- 2, mg/dL, n = 8). Serum potassium concentrations and osmolalities as well as serum creatinine levels were significantly higher in the diabetic than in the control group (5.07 +/- 0.09 vs. 4.68 +/- 0.11 mEq/L; 330 +/- 14 vs 290 +/- 3 mOsm/L; 0.40 +/- 0.03 vs 0.31 +/- 0.02 mg/dL, p < 0.05). Plasma renin activity (PRA) in the diabetic group was significantly lower than that in the control group (6.0 +/- 1.0 vs 12.1 +/- 1.1 ng Al/ml/h, p < 0.001). Plasma aldosterone concentration (PAC) was also significantly lower in the former than in the latter (368 +/- 30 vs 761 +/- 57 pg/ml, p < 0.001). Renomegaly, abnormal distal tubular cells with few organelles, and increased lipid droplets with pyknotic nucleus in zona glomerulosa of the adrenal glands were noted in the diabetic group. In conclusion, multifactorial causes including insulinopenia, hyperosmolality, elevated serum creatinine level and hypoaldosteronism with possible contribution of altered distal tubular response to aldosterone may have interacted to develop hyperkalemia in these diabetic rats.

Adrenoceptor-mediated cardiac and vascular responses in genetically growth hormone-deficient rats

This study has measured cardiovascular parameters, pharmacological responses to α and β-adrenoceptor agonists, and cardiac β-adrenoceptor characteristics in growth hormone (GH)-deficient (dwarf) Lewis rats, normal Lewis rats and dwarf rats treated with GH (2mg/kg/day for 28 days). Dwarf rats showed a decreased mean blood pressure and heart rate but an increased ventricular weight relative to body weight when compared with age-matched normal Lewis rats. Positive chronotropic responses in vivo to the non-selective β-adrenoceptor agonist, isoprenaline, were unchanged in dwarf rats. The selective β 1-adrenoceptor agonist, noradrenaline, was less potent in isolated right atria from dwarf rats although maximal responses were unchanged. Basal force of contraction was greater in isolated cardiac muscles from dwarf rats than from normal rats. Maximal positive inotropic responses to both calcium chloride and noradrenaline were reduced in left atria but increased in left ventricular papillary muscles from dwarf rats. Responses to the α 1-adrenoceptor agonist, phenylephrine, were markedly increased in isolated cardiac tissues from dwarf rats. Maximal contractile responses of isolated thoracic aortic rings from dwarf rats to KCl (100 mM) and the α-adrenoceptor agonist, noradrenaline, were markedly reduced compared to responses in normal rats. Left ventricular β-adrenoceptor density measured by 125I-cyanopindolol binding was significantly increased in dwarf rats. Administration of GH (2 mg/kg/day for 28 days) reversed the altered responses in dwarf rats. We conclude that GH: (a) is required for the development of normal contractile capability of cardiac and vascular tissues; (b) regulates both β-adrenoceptors and α- and β-adrenoceptor-mediated responses; (c) differentially regulates atrial and ventricular responsiveness.

Selective effect of chronic lead ingestion. III: Effect on dopamine beta-hydroxylase activity in brain regions of rats.

Selectivity of lead effect on dopamine beta-hydroxylase activity in regions of brai nfrom rats postnatally exposed to lead was tested. Three groups of animals were prepared; (1) Rats exposed to lead at a low dose (0.05% PbAcetate: PbAc); (2) Rats exposed to lead at a high dose (0.2% PbAc); (3) Age-matched normal control rats. At 2, 4, 6 and 8 weeks of age weight of whole brain and body in each group were measured. At the same ages activities of dopamine beta-hydroxylase and Na+K(+)-ATPase were measured in 5 brain regions of each animal. Exposure of rats to lead generally decreased Na+/K(+)-ATPase activity and showed alternative changes of dopamine beta-hydroxylase activity were detected without concomitant changes of Na+/K(+)-ATPase activity were telencephalon and pons/medulla at 2 weeks of age and telencephalon, diencephalon and pons/medulla at 4 weeks of age and midbrain and pons/medulla at 6 weeks of age and cerebellum at 8 weeks of age in rats exposed to lead at a low dose, and those in rats exposed to lead at a high dose were midbrain at 6 weeks of age and cerebellum at 8 weeks of age. These data imply that noradrenergic nervous system in the brain regions described above could selectively be affected by lead.

Selective effect of chronic lead ingestion. II: Effect on phenylethanolamine N-methyltransferase activity in brain regions of rats.

Selectivity of lead effect to phenylethanolamine N-methyltransferase (PNMT) activity in regions of brain from rats postnatally exposed to lead was tested. Three groups of animals were prepared; (1) Rats exposed to lead at a low dose (0.05% PbAcetate: PbAc); (2) Rats exposed to lead at a high dose (0.2% PbAc); (3) Age-matched normal control rats. At 2, 4, 6 and 8 weeks of age weight of whole brain and body in each group were measured. At the same ages activities of PNMT and Na+/K(+)-ATPase were examined on 4 brain regions of each animal. Exposure of rats to lead generally decreased activity of Na+/K(+)-ATPase and showed alternative change of those of PNMT. Brain regions where changes of PNMT activity were detected without concomitant changes of Na+/K(+)-ATPase activity, were telencephalon and pons/medulla at 2 weeks of age and telencephalon at 4 weeks of age in rats exposed to lead at a low dose, and those in rats exposed to lead at a high dose were pons/medulla at 8 weeks of age. These data imply that adrenergic nervous system in the brain regions described above could selectively be affected by lead.

Effect of donor islet mass on metabolic normalization in streptozotocin-diabetic rats.

The effect of donor islet mass on the metabolic normalization in streptozotocin-diabetic rats was examined by comparing normal control rats with two transplant groups receiving 800 or 2,000 islets intraportally, i.e. grafts containing respectively, 0.8 or 2 million Beta cells at 70% purity. After transplantation, basal glycaemia and daily urine volumes normalized in all recipients and remained normal in both groups over the 20-week follow-up period. After intragastric glucose challenge, the 800-islet group exceeded the normal range of glycaemia at all tested time points (0-120 min) whereas the 2,000-islet group exhibited higher glycaemia only at 15 and 30 min; no deterioration in glucose tolerance occurred during the 20-week follow-up. Both transplant groups presented lower serum fructosamine levels than diabetic control rats, normal levels being maintained only in the 2000-islet group. At post-transplantation week 21, both recipient groups exhibited the same body weight as age-matched normal control rats, but their serum triglyceride levels were significantly higher. Hepatic insulin contents were comparable to the insulin contents of the grafts at the time of implantation, representing 16 or 40% of the pancreatic insulin content in the age-matched control rats. Although islet grafts with 0.8 million Beta cells can restore basal glycaemia in adult streptozotocin-diabetic rats, implants of 2 million Beta cells are necessary to correct other parameters of glucose homeostasis. The present data indicate the need of determining the number of grafted Beta cells in studies on the metabolic outcome of islet cell transplantation. DNA content and percentage of Beta cells in the graft are proposed as useful parameters.

Selective effect of chronic lead ingestion on tyrosine hydroxylase activity in brain regions of rats.

Alterations of tyrosine hydroxylase activity in various regions of brain from rats postnatally exposed to lead were tested. Three groups of animals were prepared; (1) Rats exposed to lead at a low dose (0.05% lead acetate, PbAc); (2) Rats exposed to lead at a high dose (0.2% PbAc); (3) Age-matched normal control rats. At 2, 4, 6, and 8 weeks of age, weight of brain and body, and concentrations of lead in whole brain of animals in each group were measured. Activities of tyrosine hydroxylase and Na(+)-K+ ATPase were also measured at the same ages in 4 brain regions of each animal. Body weight gain was decreased after 6 weeks of age in rats exposed to lead at a high dose. Concentrations of lead in whole brain were increased from 0.37 to 0.83 (ng/mg wet tissue) in these animals. Exposure of rats to lead generally increased tyrosine hydroxylase activity and decreased Na(+)-K+ ATPase activity. However, changes of tyrosine hydroxylase activity were detected without concomitant changes of Na(+)-K+ ATPase activity in pons-medulla at 2 weeks of age and telencephalon at 6 weeks of age in rats exposed to lead at a low dose, and in midbrain at 4 and 6 weeks of age in rats exposed to lead at a high dose. These data imply that catecholaminergic nervous system in the brain regions described above could be selectively affected by lead.

Effects of regression of cardiac hypertrophy on myocardial contractility and ventricular myosin isoenzymes.

The effects of regression of cardiac hypertrophy on myocardial contractility and ventricular myosin isoenzymes were investigated in rats with renovascular hypertension. Six-week-old male Wistar rats were made hypertensive by constriction of one renal artery with a silver clip. Regression of cardiac hypertrophy was induced following the lowering of blood pressure by nephrectomy on the affected side 5-6 weeks after constriction of the renal artery and was maintained for 5-6 weeks. In contrast, myocardial hypertrophy was induced by 10-11 weeks of the hypertensive state. Isometric developed tension of isolated left ventricular papillary muscles was measured, while they were being perfused with Tyrode solution. Left ventricular myosin isoenzymes were separated by pyrophosphate gel electrophoresis. The ventricular to body weight ratio of the nephrectomized group was significantly lower than that of the hypertensive group, although it was greater than that of age-matched normal control rats. There were no significant differences in the isometric developed tension among three groups, the nephrectomized, hypertensive, and normal control rats. However, dT/dtmax tended to decrease in the hypertensive rats and recovered to normal in the nephrectomized rats. The left ventricular myosin isoenzyme pattern was shifted toward VM-3 in hypertensive rats and was shifted back toward VM-1 again in nephrectomized rats.

Studies on the Iodide Metabolism and the Expression of Thyroglobulin and Thyroid Peroxidase mRNA in the Thyroid of BB/W Rats

BioBreeding/Worcester (BB/W) rats develop insulin dependent diabetes mellitus (IDDM) and lymphocytic thyroiditis (LT) spontaneously. Our previous studies have shown that BB/W (Saitama-Tokyo colony) rats develop LT at about 10 weeks of age. Their serum TSH values increase as LT extends, although their serum thyroid hormone levels remain normal. This indicates that BB/W rats suffer from subclinical hypothyroidism. To investigate whether BB/W rats have a defect in iodide metabolism, the thyroidal radioactive iodine uptake (RAIU) in BB/W rats was examined. Thyroidal RAIU at 3hr in both 8 and 16 week-old BB/W rats was significantly higher than that in age-matched normal Wistar rats. On the other hand, BB/W rats had significantly lower 48hr thyroidal RAIU than normal Wistar rats. This suggests that BB/W rats appear to have some defects in iodide metabolism, especially in iodide organification even before the development of LT. The expression of thyroid peroxidase (TPO) and thyroglobulin (Tg) mRNA in BB/W and Wistar rats was then examined using the Northern blot analysis. The expression of both TPO and Tg mRNA was greatly decreased in BB/W rats compared with that in Wistar rats despite the high serum TSH levels in BB/W rats. This indicates that BB/W rats may have pretranslational defects in TPO and Tg synthesis, resulting in the impaired thyroid hormone synthesis. In the present study, it has been demonstrated that BB/W rats appear to have a defect(s) in iodide metabolism possibly due to some abnormalities in TPO and Tg synthesis.

A myo-inositol pool utilized for phosphatidylinositol synthesis is depleted in sciatic nerve from rats with streptozotocin-induced diabetes.

Peripheral nerve from experimentally diabetic rats exhibits lowered levels of myo-inositol (MI) and decreased incorporation of [3H]MI into phosphatidylinositol (PI). There are indications that diminished PI turnover may be causally related to reduced Na+,K(+)-ATPase activity in diabetic nerve. We have investigated whether a metabolic compartment of MI that is essential for PI synthesis is decreased in this tissue. Sciatic nerve segments from streptozotocin-induced diabetic and age-matched normal rats were incubated in vitro with either 32Pi or [3H]cytidine in the presence of propranolol. This cationic amphiphilic agent redirected nerve phospholipid metabolism to produce enhanced 32P incorporation into PI and decreased labeling of phosphatidylcholine and phosphatidyl-ethanolamine. The accumulation of phosphatidyl CMP (CMP-PA) was also demonstrated by chromatographic and enzymatic means. The incorporation of [3H]cytidine into CMP-PA in normal nerve increased up to 15-fold when 0.6 mM propranolol was present. In diabetic nerve, the liponucleotide incorporated 2- to 3-fold more isotope and was more readily labeled at lower drug concentrations as compared to normal nerve. The buildup of [3H]CMP-PA was reduced in a dose-dependent manner in the presence of MI in the incubation medium at concentrations up to 3 mM. However, if MI was added after liponucleotide accumulation, preformed CMP-PA could not be utilized for PI synthesis. The difference in liponucleotide labeling between normal and diabetic nerve was nearly abolished at 0.3 mM medium MI, a concentration much less than the level of cyclitol in the tissue. These results strongly suggest the presence in nerve of a pool of MI that is not in equilibrium with the bulk of nerve MI and that is preferentially used for PI synthesis. This metabolic compartment is depleted in diabetic nerve but can be readily replenished by exogenous MI and may correspond to the MI pool that has been proposed to be required for the turnover of a portion of tissue PI involved in maintenance of normal Na+,K(+)-ATPase activity.

Regulation by GH of insulin-like growth factor-I mRNA expression in rat epiphyseal growth plate as studied with in-situ hybridization

Expression of insulin-like growth factor I (IGF-I) mRNA and its dependence on GH was studied in rat epiphyseal growth plate by in-situ hybridization. Methodological aspects of the technique were first evaluated on fixed sagittal cryosections from 28-day-old rat epiphyseal growth plates to ascertain specific hybridization. In-situ hybridization was compared on sections from 10- and 28-day-old rats and the GH-dependence was studied in 35-day-old hypophysectomized rats. Expression of IGF-I mRNA was apparent in chondrocytes of the proliferative, hypertrophic and early degenerative zones of the growth plate of 28-day-old rats. The epiphyseal growth plate from 10-day-old rats showed a weak hybridization signal compared with 28-day-old rats. In contrast, the mesenchymal cells of the periosteum of 10-day-old rats showed a rather strong hybridization signal. Hypophysectomy resulted in a reduction in hybridization signal and cell number of the growth plate compared with 35-day-old age-matched normal rats. GH-Replacement therapy (200 micrograms GH s.c. every 4 h for 24 h) resulted in partially restored expression of IGF-I mRNA. The present study has shown that the IGF-I gene is expressed in the rat epiphyseal growth plate chondrocytes and that the expression is dependent on GH. The results support a paracrine/autocrine role of IGF-I for the expression of the stimulatory effect of GH on longitudinal bone growth.

Elevated mRNA levels of major histocompatibility complex class II genes in lymphocytes of autoimmune BB rats.

The BB rat spontaneously develops autoimmune abnormalities such as insulin-dependent diabetes mellitus and thyroiditis. The autoimmunity of the BB rat is controlled in part by genes of the major histocompatibility complex (MHC), known as the RT1 complex in the rat, and accumulating evidence suggests the involvement of MHC class II molecules. The RT1 complex specifies two types of class II molecules, which are encoded by the loci RT1.B and RT1.D. We have determined the relative steady-state mRNA levels of the class II genes RT1.B beta, RT1.D alpha, and RT1.D beta in splenic lymphocytes from individual autoimmune BB rats of various ages and from age-matched histocompatible normal Wistar-Furth (WF) rats. The relative steady-state mRNA levels of the RT1.D alpha and RT1.D beta genes, but not of the RT1.B beta gene, were elevated approximately 2.5-fold in lymphocytes of prediabetic BB rats 45-75 days old in comparison with age-matched normal WF rats and older BB rats greater than 75 days old. In the diabetic and nondiabetic BB rats greater than 75 days old, the RT1.D alpha and RT1.D beta transcripts were found at lower normal levels, similar to that of WF rats. In contrast, the RT1.B beta transcripts were found at comparable levels in lymphocytes of the BB and WF rats at all ages examined. The increased steady-state mRNA levels of the RT1.D alpha and RT1.D beta genes in the prediabetic BB rats may reflect differences in the proportion of lymphocytes expressing these genes and thus differences in splenic lymphocyte populations.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of irradiation on cortical bone and their time-related changes. A biomechanical and histomorphological study.

The effects of high-dose irradiation on the biomechanical and morphological properties of cortical bone and their time-related changes were studied in male Sprague-Dawley rats. A single fraction of 3500 rads was applied to the middle part of the right thigh. Age and sex-matched control rats that did not receive radiation were used for comparison. Two weeks after irradiation, the animals had lost weight and disappearance of bone cells, shrunken osteocytes, and significantly decreased bone-turnover activities were noted. The bone marrow showed reduced hematopoietic elements and sinusoids with increased fat. No change in the torsional strength and geometric properties of bone was noted at this time. Six to ten weeks after irradiation, histopathological abnormalities of the bone persisted, and there was an accelerated resorption process. However, significant increases in the strength and cortical area of bone appeared only in the non-irradiated, contralateral femur. On the irradiated side, decreased cortical area and increased porosity of bone were found at fourteen to eighteen weeks when compared with the control rats. Other histomorphological properties, such as bone porosity, osteocyte count, and periosteal new-bone formation, appeared to recover eighteen weeks after irradiation, as they became similar to the values for the age-matched normal control rats.

Antihypertensive drugs inhibit hypertension-associated aortic DNA synthesis in the rat.

The effect of antihypertensive drug treatment on aortic DNA synthesis was examined in rats with two-kidney, one clip renal hypertension and in spontaneously hypertensive rats (SHR). In two-kidney, one clip hypertensive rats, hypertension developed over a 2-week period. Four days after clipping the renal artery, during the onset of hypertension, there was an increase in aortic DNA synthesis. Aortic DNA synthesis was also increased 3 weeks later, when hypertension had been established. Captopril, hydralazine, and verapamil were each able to prevent the increase in aortic DNA synthesis and the rise in blood pressure when given throughout the first 5 days of the developing phase of hypertension, or when given to rats with established hypertension. Drug treatment of sham-operated rats had no significant effect on DNA synthesis, although blood pressure was decreased. There were no differences in blood pressure or aortic DNA synthesis in 4-week-old SHR, as compared with age-matched Wistar-Kyoto (WKY) controls or normal Wistar rats. At 17 weeks of age, when hypertension was established, aortic DNA synthesis was significantly enhanced in the SHR. Captopril or hydralazine treatment was able to reduce blood pressure and DNA synthesis to levels seen in the WKY. At 21 weeks of age, DNA synthesis in the SHR had declined to the same levels as in the WKY. Captopril, hydralazine, and verapamil may have a common ability to reduce intracellular calcium and therefore inhibit DNA synthesis. In support of this, ouabain treatment, which increases intracellular calcium by inhibiting the Na+-K+ pump, produced a significant increase in the rate of DNA synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Longitudinal study of first phase insulin release in the BB rat.

First phase insulin release was measured in response to intravenous glucose given weekly from approximately day 40 in 6 BB rats which subsequently developed diabetes and in age-matched non-diabetic (n = 15) and normal Wistar rats (n = 8) until day 180. The mean sequential insulin responses in BB rats with and without diabetes were significantly lower (p = 0.008 and less than 0.0001, respectively) than in normal rats from an early age. Five diabetic BB rats showed a progressive decline in first phase insulin release immediately prior to glycosuria, with the impaired phases ranging from 25-50 days. However, protracted periods of low first phase responses were also seen in several aglycosuric BB rats, which showed histological evidence of insulitis and B-cell loss. Our findings demonstrate that, although most BB rats with diabetes show a progressive impairment of B-cell function preceding the disease, this aberrant phase can also be present in BB rats which remain aglycosuric. Impaired first phase insulin release in response to serial intravenous glucose tolerance tests may not be a reliable predictor of Type 1 (insulin-dependent) diabetes in this animal model.

Prevention of diabetic glomerulopathy by pharmacological amelioration of glomerular capillary hypertension.

Two groups of adult male Munich-Wistar rats and a third group of nondiabetic age-matched and weight-matched normal control rats underwent micropuncture study 1 mo, and morphologic studies 14 mo, after induction of streptozotocin diabetes or sham treatment. All animals were fed standard rat chow. Diabetic rats received daily ultralente insulin to maintain stable moderate hyperglycemia (approximately 350 mg/dl). In addition, one group of diabetic rats was treated with the angiotensin I converting enzyme inhibitor, enalapril, 15 mg/liter of drinking water. Average kidney weight, whole kidney and single-nephron glomerular filtration rate, and glomerular plasma flow rate were elevated to similar values in both groups of diabetic rats, relative to normal control rats. Non-enalapril-treated diabetic rats exhibited significant elevations in mean glomerular capillary hydraulic pressure and transcapillary hydraulic pressure gradient, compared with the other groups studied, and only this group eventually developed marked and progressive albuminuria. Likewise, histological examination of the kidneys at 14 mo disclosed a high incidence of glomerular structural abnormalities only in non-enalapril-treated diabetic rats. These findings indicate that prevention of glomerular capillary hypertension in rats with diabetes mellitus effectively protects against the subsequent development of glomerular structural injury and proteinuria. This protection is afforded despite pronounced hyperglycemia and elevated levels of glucosylated hemoglobin, further supporting our view that hemodynamic rather than metabolic factors predominate in the pathogenesis of diabetic glomerulopathy.

Heart myosin light chain 2 gene. Nucleotide sequence of full length cDNA and expression in normal and hypertensive rat.

We have isolated and characterized a cDNA recombinant plasmid (pRLC429) specific for the rat heart myosin light chain 2 (MLC2). The cDNA insert consists of 446 base pairs, including a 72-base pair segment of the 3'-untranslated region. Additional 5'-sequence, not present in plasmid pRLC429, was obtained by primer extension of the cDNA. The extended cDNA sequence combined with the plasmid pRLC429 sequence provided the codon information for the entire MLC2 polypeptide and partial sequences for the 3'- and 5'-noncoding regions of MLC2 mRNA. The predicted amino acid sequence for rat heart MLC2 showed a high homology with the sequences available for the chicken (83%) and human heart (80%) MLC2s. However, the homology between rat heart MLC2 and its counterpart in rat skeletal muscle is relatively low (67%). On the basis of the nuclease S1 protection assay with uniformly labeled single-stranded pRLC429 DNA, subcloned into M13mp18 phage vector, we conclude that the rat atrial muscle also contains MLC2 of the ventricular type. In an attempt to ascertain whether structural variants of MLC2 are expressed in hypertrophic heart muscle, we examined the RNAs from spontaneously hypertensive rat where there is a natural progression of hypertrophy associated with an increase in blood pressure. The RNA isolated from 7-, 13-, and 18-week-old spontaneously hypertensive rat hearts protected the same length DNA against S1 nuclease as was observed with RNAs from the age-matched normal rat hearts, suggesting that there is a single MLC2 gene transcript expressed in both the normal and hypertrophic heart muscle cells.

Structure and function of orthotopic small bowel allografts in rats treated with cyclosporine

Previous studies of small bowel transplantation using a variety of animal models and immunosuppressive regimens have failed to demonstrate consistently prolonged survival of bowel allografts capable of maintaining a normal nutritional state. In the present study, total orthotopic small bowel transplantation was performed in inbred rat strains to determine the structure and function of intestinal allografts using cyclosporine for immunosuppression. Without cyclosporine, Lewis-Brown Norway and Brown Norway allografts were quickly rejected by Lewis recipients, resulting in host death. A 15 mg/kg dose of cyclosporine given intramuscularly immediately after operation and for 6 successive days thereafter achieved prolonged but not uniformly indefinite animal and graft survival with clinical courses and pathologic findings consistent with chronic rejection. With continuation of cyclosporine every other day until day 28, all Lewis recipients of Brown Norway allografts were alive and well 8 months after transplantation. Weight gain, maltose absorption, and multiple nutritional indices in these animals were not significantly different from those of either age-matched normal Lewis rats or recipients of Lewis isografts. Full-thickness biopsy specimens of these allografts showed no evidence of graft rejection. These results demonstrate that indefinite survival of intestinal allografts with preservation of their structure and function sufficient to allow normal growth and weight gain can be achieved with cyclosporine therapy. This success in the rat model of orthotopic small bowel transplantation suggests that clinical small-bowel transplantation may become possible using cyclosporine.