Diabetes in Chinese hamster was initially detected by qualitative tests for urine ~lucose. The disease was ct~aracterized by quantitating urine glucose, glucose tolerance tests and measurement of fasting and nonfasting blood sugar, blood ketones, plasma free fatty acids (FFA), plasma insulin, pancreatic insulin and fasting levels of liver glycogen. In addition, basal levels of glucose utilization by diaphragms and epididymal adipose tissue and the response of these tissues to insulin was measured. Those animals requiring insulin received their last injection 24 hours prior to study. Glucosuria varied from 51 to 1600 mg/24 hours. Diabetics had significantly decreased tolerance to a 250 mg/kg glucose load. The response varied considerably in diabetics but was uniform in the nondiabetics. Diabetics had mean fasting liver glycogen levels of 3.1 :~ 1.0 compared with 0.4 --0.7 percent of fresh liver weight for nondiabetics. Severely ketotic, diabetic Chinese hamsters had significantly elevated FFA and ketone levels and significantly lower plasma and pancreatic insulin levels but mild diabetics did not differ from controls with respect to these parameters. Alt Chinese hamsters had high plasma FFA levels (nondiabeties 1800 teE/l, severe diabetics 2800 teE/l). Fasting and nonfasting FFA levels did not differ in mild diabetic and nondiabetie animals. Muscle and adipose tissues from diabetic hamsters had basal rates similar to nondiabetics and had similar responses to insulin. Hamsters maintained on insulin had greatly elevated immunoreaetive insulin levels in their plasma, which persisted for 26 days. --The data suggest that severely diabetic hamsters may have a decreased ability of the pancreas to secrete insulin in response to a glucose stimulus. The observations that plasma insulin levels are normal in mild diabetics but that these animals have glucosuria, hyperglycemia and abnormal glucose tolerance suggest that mild diabetes in the Chinese hamster may involve interference with insulin action and/or increased hepatic glucose output.Caract~risation du diab~te du hamster chino@. Vol. 3, No. 2, 1967 G.C. GERaITS]~ and W.E. DuLI~<: Diabetes in the Chinese Hamster 75 ist noch 26 Tage nach der letzten Injektion nachweisbar. --Diese Ergebnisse lessen vermuten, dal~ dcr Pankreas des diabetischen Hamsters nur schwerlich in der Late ist, naeh ether Glucosestimulierung Insulin auszuschiitten. Die Beobachtung, dal~ der Plasma-Insulinspiegel im leithten Diabetes normal ist, diese Tiere jedoch Glucosurie, Hyperglyk~mie and abnormale Glucosetoleranz aufweisen, fiihrt zu der Annahme, dal3 ein leichter Diabetes beim chinesisehen Hamster eine Beeintr~ichtigung der Insulinwirkung mit sich bringen, und Ursache einer vermehrten Glucoseproduktion durch die Leber sein kalm.

Therefore, to characterize pancreatic islet function, dynamic insulin and glucagon release from normal and nonketotic diabetic hamster pancreases in response to glucose (300 mg/100 ml) and theophylline (10 mM), infused singly and together, was studied in vitro.20-min glucose infusions of normal hamster pancreases caused biphasic insulin release, consisting of a rapid first peak and a gradually rising second phase, similar to that reported for man in vivo. Both phases were significantly reduced in the diabetic pancreases. Theophylline alone stimulated similar nonphasic insulin release in both the normal and the diabetic pancreases. Glucose and theophylline together caused greater insulin release than either stimulant alone in both normals and diabetics; however, the diabetic response was still subnormal.Glucose suppressed glucagon release from normal pancreases; suppression was significantly impaired in diabetics. Theophylline stimulated nonphasic glucagon release in both the normals and diabetics. Glucose partially suppressed the theophylline-stimulated release in both groups.Insulin/glucagon molar ratios of the diabetics were consistently subnormal, although individual hormone levels often overlapped into the normal range.This work was presented in part at the Western Section of the American Federation for Clinical Research, Carmel, Calif., 2 February 1973 (Clin. Res. 21: 273)

Selection for and against diabetes and subsequent inbreeding of Chinese hamsters started in 1963. Currently there are six inbred sublines that have greater than 85% incidence of glycosuria and two control inbred nondiabetic sublines that are essentially free of glycosuria. At birth, hamsters from inbred sublines are considered prediabetic. There is phenotypic variation between diabetic sublines. Onset time, incidence of ketonuria, blood glucose, plasma insulin, glucagon and glycohydrolase levels vary from subline to subline, but pancreatic insulin and glucagon levels are consistently low and high, respectively, in all diabetic sublines compared with nondiabetics. Experimental breeding data suggest a minimum of two homozygous recessive genes for diabetes. It is not known if the inbred lines are similar diabetic genotypes, but the probability is high that modifier background genes vary from subline to subline.Chinese hamsters have diabetes ranging from mild to severe. Animals weighing 25 g can excrete up to 75 ml of urine containing 3 g of glucose per day. Fasting blood glucose as high as 500 mg/dl and 10 /nmol/ml of beta-hydroxybutyrate have been reported. Gluconeogenesis is elevated, and some glycolytic enzymes are decreased in severe diabetes. Low levels of renal acid glycohydrolase enzymes may contribute to glomerular capillary loop basement membrane thickening in diabetic hamsters. Caloric restriction per se or reduction of dietary fat prevented onset of hyperglycemia and hyperinsulinemia in prediabetics. Morphologic changes have been observed in pancreatic islets, kidney, nerve, blood vessels, eyes, brain, and genitourinary systems of diabetic Chinese hamsters. Pathogenesis of diabetes in this animal appears to be related to an increased demand for insulin. Initially there is a positive response to this demand by beta cells, but exhaustion occurs. This is followed by a decrease in beta-cell mass and relative or absolute insulin deficiency. DIABETES 37 (Suppl.

The relationship between diabetes and the morphological alterations which occur in hypothalamic and ovarian tissue was examined in the long-term, ketonuric-diabetic Chinese hamster. Matched diabetic and non-diabetic control hamsters were inspected daily for changes in the reproductive cycle by vaginal lavage. On dioestrus, animals were perfused, the hypothalamus and ovaries collected, prepared for microscopy and morphometrically analyzed. The nuclei in the medial basal hypothalamus of diabetic hamsters exhibited a decreased area (p less than 0.01) and neuronal population (p less than 0.05-0.01) compared with controls. The ovaries of the diabetic animals had a reduced follicular population (p less than or equal to 0.05) and an increased atresia rate (p less than or equal to 0.05) compared with controls. In addition, all diabetic hamsters were acyclic. In diabetic animals, the corpora luteal cells contained a reduced lipid content (p less than or equal to 0.001) which was possibly functionally related to a significant decline in serum progesterone levels (p less than or equal to 0.01). Based on these results it is suggested that the hypothalamic-ovarian axis is both morphologically and functionally impaired in the diabetic hamster.

No abstract

As a hypoglycemic agent, 3,5-dimethylpyrazole (U-6245) was found to be fifty-four times more potent orally than tolbutamide in glucose-injected, fasted intact rats. U-6245 increased glucose oxidation by intact rats. It lowered plasma free fatty acids but not blood sugar of eviscerate rats and was effective in decreasing the fasting bloodsugar levels of alloxan-diabetic rats which were unresponsive to tolbutamide. U-6245 markedly depressed plasma FFA fifteen minutes to three hours after its administration. The mechanism of hypoglycemic activity of 3,5-dimethylpyrazole is not the same as insulin, sulfonylureas or biguanides in that: (1) It is ineffective in lowering the blood sugar of eviscerates while insulin is. (2) U-6245 is active in alloxan diabetic rats which are unresponsive to tolbutamide. (3) The pyrazole increases glucose oxidation and biguanides do not. Although the mechanism of action of 3,5-dimethylpyrazole is not understood, data are presented which support the hypothesis that its action may depend on its effect on plasma FFA and also on the presence of the liver and/or intestinal tract. Since the pyrazole increases glucose oxidation in intact rats, it appears that at least part of its action may be due to the stimulation of glucose oxidation by the intestinal tract and/or liver.

No abstract

The relationship between diabetes and the size, density and area of the ventromedial hypothalamic nucleus (VMH) was studied in the genetically diabetic Chinese hamster. Matched diabetic and non-diabetic control chinese hamsters were perfused, the hypothalamus collected, sectioned and stained for light microscopy. The mid-point of each VMH nucleus was located, photographed and enlarged for morphometric analysis. Each neuron that possessed a nucleolus and was located within the confines of a VMH was counted, and subsequently the area of each nucleus and the density of neurons per area of VMH were calculated. The results indicated that both the area and absolute number of neurons within the VMH of diabetic hamsters were significantly reduced compared to control values (P less than 0.01) The density of neurons per unit area of VMH was similar in both groups. These data suggest that the VMH experiences a neuronal depopulation in diabetic hamsters which may have a functional influence on the hypothalamic-pancreatic axis in this species.