Atrial natriuretic peptide in dehydrated Long-Evans rats and Brattleboro rats

Atrial natriuretic peptide (ANP) was measured by radioimmunoassay in atrial and plasma extracts from normal Long-Evans (LE) rats and Brattleboro-strain diabetes insipidus (DI) rats. LE rats, dehydrated for 72 hours, had an increased plasma osmolality and plasma vasopressin. They also demonstrated a higher atrial immunoreactive ANP (IR-ANP) content than hydrated animals (72 hr dehydration: 178.2 +/- 30.4 micrograms/g wet weight atria, mean +/- SE, control: 60.4 +/- 8.2; P less than 0.001). Plasma IR-ANP in dehydrated LE rats tended to be lower than hydrated LE but this was not statistically significant [72 hr dehydration: 61.9 +/- 5.9 pg/ml, control: 82.4 +/- 8.2]. IR-ANP concentration in atrial extracts from DI rats, without detectable plasma vasopressin levels but with increased plasma osmolality, was not different from that in hydrated LE rats (DI: 100.6 +/- 13.2 micrograms/g). There was also no significant difference between plasma IR-ANP in DI and hydrated LE rats (DI: 100.2 +/- 11.9 pg/ml). The atrial IR-ANP concentration in DI rats was decreased by infusion with either arginine-vasopressin (AVP) or 1-deamino-8-arginine vasopressin (DDAVP), and plasma IR-ANP was increased significantly by both infusions (AVP: 171.3 +/- 18.1 pg/ml, DDAVP: 179.5 +/- 24.6). Thus, changes in atrial and plasma IR-ANP concentration appeared to be associated with changes in water balance but not with plasma AVP levels, indicating that the changes in volume may be a more important factor controlling ANP release in vivo than vasopressin itself.     

Vasography in rats

Vasovasostomy was performed in 20 rats. Vasography then was used to determine the patency of the vas. The scrotum was entered through a longitudinal incision and the scrotal contents were extruded extravaginally. The vas was divided near the epididymis and a 0.4/0.7-mm cannula was inserted into the abdominal end of the vas and contrast medium was injected under fluoroscopic control. The results were documented by radiography. It is concluded that vasography is a reliable method for assessing the success of vasovasostomy in rats.     

Comparative morphometric analysis of cochlear vessels in Wistar-Kyoto rats, spontaneously hypertensive rats, and aged spontaneously hypertensive rats

Vessel density and the ratio of the tissue area to the vessel surface area were studied by morphometric analysis techniques in normal rats, spontaneously hypertensive rats (SHR), and aged spontaneously hypertensive rats (aged SHR). Horseradish peroxidase was injected intravenously and the animals were killed 10 minutes later. The temporal bones were harvested, fixed in glutaraldehyde, and decalcified in 10% ethylenediamine tetraacetic acid (EDTA). After 7 days of decalcification, the cochleas were dissected and incubated with a diaminobenzidine tetrahydrochloride solution. Sections with stained vessels were projected onto the digitizing plate with the help of the camera lucida. The computer was used to calculate tissue area, vessel length, and vessel surface area. A statistically significant increase (p less than 0.05) in both the tissue area to vessel length ratio and the tissue area to vessel surface area ratio was demonstrated in the SHR and the aged SHR groups when compared to the WKY in the stria vascularis. No statistically significant difference was found between the two SHR groups. These data show a decrease of the vessel density in the capillary beds of the stria vascularis in spontaneously hypertensive rats. No statistically significant difference was found in the diameters of the capillary among the three groups.     

Glucose-6-phosphate dehydrogenase in kidneys of lead-poisoned rats and adrenalectomized rats

Glucose-6-phosphate dehydrogenase (G6PDH) activity, assayed biochemically, was significantly increased in kidney homogenates of lead-poisoned rats when compared with controls. Histochemically, G6PDH activity was greatly increased both in the distal tubules and the macula densa, but showed no significant changes in the proximal tubules. Biochemical assay of G6PDH in kidney homogenates of adrenalectomized rats was three times that in control animals. In this condition also, histochemical staining showed G6PDH activity to be increased in both macula densa and distal tubules. This demonstrates an increase in G6PHD in two completely different experimental conditions and suggests that the distal renal tubule in the rat might operate in functional unity with the macula densa.     

Experimental vaginitis in rats

The authors present an experimental model of vaginal inflammation in female rats, through local instillation of different substances causing inflammation of varying degrees. The inflammatory reaction was studied macroscopically, histologically and biochemically. Using polysiloxane as a protective substance of vaginal mucosa was found to be of therapeutic interest.     

Intramuscular urography in rats

In addition to macroscopic studies, microscopic studies, and biologic tests, urography is a valuable method for investigating renal function in rats. Intravenous urography is complicated, however, by the difficulty of puncturing a tail vein or the femoral vein. Intramuscular urography, on the other hand, is a simple and reliable method for radiographic examination of the kidneys and ureters, and gives information on morphology as well as physiology. In this study in 40 rats, intramuscular urography was performed under general anesthesia, and the contrast medium was injected into the gluteal muscles. Dense nephrograms and optimum films of the calices and the ureters were obtained approximately 40 minutes after injection.     

Morphine-halothane interaction in rats

The effects of morphine, halothane, and their various combinations on the purposeful movement (PM) response and the heart rate (HR) increase caused by noxious stimulation were studied in 250 rat experiments. Doses that block the PM and HR responses for the single agent and for combinations were determined with a probit procedure and compared with an isobolographic analysis. As was evidenced by the PM response, the combined anesthetic effect of morphine and halothane, with some deviations, may be defined as additive. It also was found that the combined administration of morphine and halothane results in an antagonism for suppression of the HR increase to noxious stimulation. Halothane antagonized morphine to a much greater extent than morphine to halothane.     

Genetic hypercalciuric stone-forming rats

PURPOSE OF REVIEW: We will describe the pathophysiology of hypercalciuria and the mechanism of the resultant stone formation in a rat model and draw parallels to human hypercalciuria and stone formation. RECENT FINDINGS: Through inbreeding we have established a strain of rats that excrete 8-10 times more urinary calcium than control rats. These genetic hypercalciuric rats absorb more dietary calcium at lower 1,25-dihydroxyvitamin D3 levels. Elevated urinary calcium excretion on a low-calcium diet indicated a defect in renal calcium reabsorption and/or an increase in bone resorption. Bone from hypercalciuric rats released more calcium when exposed to 1,25-dihydroxyvitamin D3. Bisphosphonate significantly reduced urinary calcium excretion in rats fed a low-calcium diet. Clearance studies showed a primary defect in renal calcium reabsorption. The intestine, bone and kidneys of the hypercalciuric rats had increased numbers of vitamin D receptors. When hydroxyproline is added to their diet they form calcium oxalate stones, the most common stone type in humans. Increased numbers of vitamin D receptors may cause hypercalciuria in these rats and humans. SUMMARY: Understanding the mechanism of hypercalciuria and stone formation in this animal model will help clinicians devise effective treatment strategies for preventing recurrent stone formation in humans.     

Lumbar microdiscectomy in rats

An operative method for lumbar microdiscectomy in rats is described in general terms so that it may be adapted to any microsurgical laboratory. The operation may be used as an advanced exercise in microsurgery, or to prepare surgeons for clinical lumbar microdiscectomy surgery.     

Production of methylguanidine from creatinine in normal rats and rats with renal failure

Creatinine (Cr) was administered intraperitoneally to both normal rats and those given adenine, and time-course changes in methylguanidine (MG) production from Cr were compared. In rats with renal failure, the accumulation of MG in the body increased gradually with time after Cr administration. In particular, the MG level in skeletal muscle was markedly high in comparison with that in serum, liver or kidney, and a high concentration of MG was still present 24 h after Cr loading. In contrast, the amount of MG excreted into urine in these rats during 24 h after Cr administration was lower than the corresponding values in normal rats. Thus, the amount of MG per rat, distributed at 24 h after intraperitoneal administration of Cr 300 mg/100 g body weight was calculated. The production of MG from Cr was found to be markedly higher in rats with adenine-induced renal failure (172.09 micrograms/100 g body weight) than in normal rats (70.30 micrograms/100 g body weight). Produced MG was mostly excreted into urine in normal rats, whereas in rats with renal failure as much as 79.1% of produced MG was accumulated in the body.     

Transplantation of pancreatic islets from hypothalamic obese rats corrects hyperglycemia of diabetic rats

Pancreatic islets isolated from adult obese rats, obtained by neonatal treatment with monosodium L-glutamate (MSG), oversecrete insulin stimulated by glucose concentration. Whereas adult MSG obese rats are hyperinsulinemic, their pancreatic islets still secrete insulin after high glucose demand. This is crucial so that the animals do not become hyperglycemic. Islets from MSG obese rats were implanted in diabetic donor rats so that the capacity of islets in regulating blood glucose concentration could be evaluated. Hyperglycemic (glucose 22 to 34 mmol/L) rats obtained with streptozotocin (STZ) treatment were used as recipients. Islet donors consisted of control adult and MSG obese rats. Only 600 islets were transplanted via the portal vein to diabetic rats. During 4 days after the transplant, fed blood glucose was monitored. After 12 hours of fasting the rats were killed; their blood samples were used to measure glucose and insulin concentration; retroperitoneal fat pads were isolated and weighed to estimate body fat. Transplanted islets from MSG obese rats decreased of fed glucose levels by 34% in diabetic rats (P < .05); however, glucose levels still remained twofold higher than those of intact controls (P < .05). Similar to MSG islets, islets grafts from control rats provoked the same effects in diabetic rats. High fasting blood glucose and low insulin levels of diabetic rats were corrected by islet grafts. Transplantations were able to recover 40% of fat in diabetic rats. The results demonstrated that islets from MSG obese rats may regulate blood glucose concentrations in diabetic rats, and suggesting that their function was not permanently altered by the onset of obesity.     

Genetic studies in inbred BB/Wor rats. Analysis of progeny produced by crossing lymphopenic diabetes-prone rats with nonlymphopenic diabetic rats

BB/Wor diabetes-prone (DP) rats are lymphopenic and frequently develop insulin-dependent diabetes. Diabetes-resistant (DR) BB/Wor rats are not lymphopenic and become diabetic rarely and at a significantly younger age. To examine the genetic basis for diabetes, lymphopenia, and age at onset of diabetes among inbred BB/Wor rats, we crossed nonlymphopenic diabetic rats with lymphopenic DP animals and studied F1, F2, and backcross progeny. F1 rats were neither diabetic nor lymphopenic. Diabetes (both types) and lymphopenia reappeared among F2 rats, confirming the permissive association of diabetes and lymphopenia and the recessive nature of both. The absence of diabetes in F1 rats also suggested that the combination of genes responsible for diabetes among lymphopenic and nonlymphopenic rats may be distinct. Nonlymphopenic parental, F1, and F2 rats revealed normal lymphocyte subsets, including CD8+ and RT6+ T-lymphocytes. Lymphopenic parental and F2 rats revealed the absence of CD8+ and RT6+ cells, indicating that these T-lymphocyte abnormalities of lymphopenic DP rats segregate with the lymphopenia gene. The distribution of the ages at onset of diabetes among F2 lymphopenic and F2 intercross rats was significantly earlier than among lymphopenic parental and backcross animals, suggesting that the age of diabetes onset is a heritable trait and that the gene(s) or genetic modifier(s) responsible for the earlier onset of F2 diabetes was acquired from the nonlymphopenic parents. Our genetic studies also confirmed the observations that the 2- and 7-kilobase Bam HI fragments of the MHC class I region do not correlate with diabetes or lymphopenia.     

慢病毒介导的RNA干扰对醛固酮过负荷心肌梗死大鼠心脏重构的影响

目的 观察慢病毒介导的p38丝裂原活化蛋白激酶(p38MAPK)短发夹RNA(PGLV-shRNA)对醛固酮过负荷大鼠心肌梗死后心脏重构的影响并探讨其机制.方法 制作醛固酮过负荷大鼠心肌梗死模型(左室射血分数48.63±6.43),构建PGLV-shRNA经尾静脉注射,超声评价心脏重构,检测心肌胶原容积分数(CVF)、p38 MAPK、结缔组织生长因子(CTGF) mRNA及蛋白的表达.结果 醛固酮过负荷大鼠心肌梗死后心脏收缩功能显著降低(48.63±6.43比64.62 ±7.90;P＜0.01),伴CVF增加,p38MAPK、CTGF蛋白表达显著上调(P＜0.01).PGLV-shRNA明显改善心肌梗死后的心脏重构,减少CVF(36.55 ±6.31比58.62±7.60;P＜0.05)、p38MAPK mRNA和蛋白、CTGF mRNA和蛋白表达(0.42±0.06比0.60 ±0.12;P＜0.05).结论 醛固酮过负荷大鼠心肌梗死后心脏重构与p38MAPK信号通路介导的心肌细胞纤维化相关,PGLV-shRNA抑制心肌细胞纤维化,改善心肌梗死后的心脏重构.     

Carbohydrate metabolism in potassium-depleted rats

Carbohydrate metabolism was examined in different organs of rats with dietary potassium deprivation for 4 weeks. Thereafter, a 24- or 48-hour starvation period caused a significant decrease of skeletal muscle and liver glycogen content in K+-depleted (KD) rats, whereas kidney glycogen concentration increased and heart glycogen remained unchanged. In contrast, liver glucose concentration was significantly higher in starved KD animals without changes in muscle, heart, and kidney glucose concentrations. Potassium depletion caused a highly significant decrease of plasma and muscle potassium concentrations, metabolic alkalosis, reduced plasma insulin, and increased creatine phosphokinase levels. Blood lactate, pyruvate, and oxoglutarate levels were significantly enhanced in fasted KD rats, whereas blood citrate, beta-hydroxybutyrate, and glucose concentrations were unchanged. Blood acetoacetate level, however, was significantly reduced following potassium depletion. Therefore, beta-hydroxybutyrate/acetoacetate ratio increased significantly, whereas lactate/pyruvate ratio was not influenced. Our results clearly indicate impaired carbohydrate metabolism in potassium-depleted rats.     

Experimental renal hypertension in rats

The present study has been concerned with blood pressure, renal functions and the microscopic changes of the kidney during permanent hypertension induced by unilateral ligation of the renal artery.