Preliminary studies on food and water consumption of prediabetic Chinese hamsters

Insulin, glucagon, and somatostatin release from the prediabetic Chinese hamster

Diabetes mellitus in the adult Chinese hamster is characterized by subnormal pancreatic insulin release in vitro, decreased insulin content, and lack of obesity. The cause of the islet B-cell failure is not clear. We measured insulin, glucagon, and somatostatin release from in vitro perfused pancreases of young (mean age 10 and 20 weeks), genetically diabetic animals (subline AC, mean plasma glucose 8.0 and 16.6 mmol/l, respectively). Compared to age- and sex-matched normal hamsters (subline M, mean plasma glucose 5.3 mmol/l), the younger diabetic animals had a significantly elevated mean plasma glucose level, but net in vitro pancreatic release of insulin, glucagon, and somatostatin was normal. Pancreatic content of insulin and glucagon was also not significantly different from normal. At age 20 weeks, when the plasma glucose of the diabetic animals was even more elevated, pancreatic content and release of insulin were significantly subnormal, whereas glucagon and somatostatin release were normal, and pancreatic content of glucagon was normal. In a similar group of young (mean age 10 weeks) diabetic animals, non-fasting plasma insulin levels were within the normal range, but the corresponding glucose levels were excessive in most of the animals (13 out of 19). In conclusion, 10-week-old diabetic hamsters show mild hyperglycaemia which cannot be accounted for directly by decreased pancreatic release in response to a glucose plus arginine stimulus in vitro. Decreased ability of the B cell to respond in vivo to hyperglycaemia or peripheral resistance to insulin may contribute to later B-cell failure in the older diabetic hamster.

Experimental hypothalamic or genetic obesity in the non-insulin-dependent diabetic rat

Non-insulin-dependent diabetes was obtained in adult rats by neonatal administration of streptozotocin (100 mg/kg). Obesity was obtained in the same animals either by a ventromedial hypothalamic lesion in adult non-insulin-dependent diabetic Wistar rats, or by using genetically obese Zucker rats. In diabetic rats, weight gain was similar to that in non-diabetic rats, whether hyperphagia was due to a ventromedial hypothalamic lesion or to a genetic factor. Glucose-induced insulin release in vivo was increased in obese diabetic rats compared with non-diabetic rats. Despite this enhanced insulin secretion, both diabetic 'fatty' Zucker rats and diabetic rats with hypothalamic obesity showed a deterioration of glucose tolerance. Moreover, about one-third developed overt diabetes with permanent or transient glycosuria. We conclude that when insulin-deficient rats are made hyperphagic, they are able to increase their insulin secretion and become obese. In some of these animals the occurrence of obesity aggravates the diabetes. The obese diabetic rat appears to be a suitable laboratory model for the study of the relationship between obesity and diabetes.

Wound healing in normal and diabetic Chinese hamsters

Wound healing was examined in normal and diabetic, non ketotic Chinese hamsters by morphological and morphometric methods. Dermal, perforating wounds were made in the ears of the hamsters and the response to injury was evaluated in tissue biopsies. The response in normal hamsters was characterized by vascular and cellular migration and pronounced infiltration of polymorphonuclear leukocytes into the area closest to the wound (zone 1). The transition region (zone 2) between wounded and non-wounded tissue was infiltrated primarily by fibroblasts and capillaries. In wounds from diabetic hamsters, 8 h after injury, there was less cellular infiltration (fibroblasts 49%, polymorphonuclear leukocytes 48% of control) and vascular proliferation (47% of control). In the late phase of healing (16 h after injury) the vascular (87% of control) and polymorphonuclear leukocyte (103%) responses in diabetic wounds were not significantly different from control in zones 1 and 2. Wounds from diabetic hamsters also showed considerable oedema (143% of control) in zones 1 and 2, which was accompanied by vascular degeneration and necrosis. At 16 h the collagen content of diabetic wounds was also decreased (54% of control). Increased oedema with reduced vascular proliferation and cellular infiltration in the early healing period characterises the response to injury in the diabetic Chinese hamster.

Chemical diabetes in the adult rat as the spontaneous evolution of neonatal diabetes

Injection of streptozotocin in newborn rats induced a severe diabetic syndrome on day 4 after birth, with acute hyperglycaemia and glycosuria. Over the next 3 weeks spontaneous recovery occurred as attested by normal basal blood glucose and plasma insulin levels. Recovery was, however, incomplete in the adult since a definite impairment in insulin release and glucose disposal was observed. This state was characterized by the following features: 1) a 72% decrease in pancreatic insulin stores without change in pancreatic glucagon stores; 2) a slight but consistent elevation of blood glucose in the fasted and fed basal states and especially of blood glucose 90 min after an IV glucose load (2 g/kg) performed under pentobarbitone anaesthesia; 3) a considerable decline in the glucose-induced insulin release with a decrease in the maximal response. Both early and late phases of insulin release were impaired, as indicated by in vivo glucose infusion experiments. Basal plasma glucagon levels were normal. Over a period of 12 months with a normal laboratory diet no aggravation of the chemical diabetic state was observed. This new experimental syndrome is a potentially interesting model for the study of the influence of environmental factors on the development of overt diabetes.

Abnormal secretion of insulin and glucagon by the in vitro perfused pancreas of the genetically diabetic Chinese hamster

Hereditary insulin-deficient diabetes mellitus occurs in certain sublines of nonobese Chinese hamsters. Several characteristics of this syndrome are similar to those seen in insulin-deficient human diabetics. 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. IN SUMMARY, THE PANCREASES OF GENETICALLY DIABETIC CHINESE HAMSTERS PERFUSED IN VITRO SHOWED: (a) decreased first and second phase insulin release in response to glucose-containing stimuli-only partially ameliorated by theophylline-, and (b) impaired suppression of glucagon in response to glucose, resulting in (c) a decreased insulin/glucagon molar ratio. These data support the suggestion that both alpha and beta cells of diabetic pancreases may be insensitive to glucose.