Diabetogenic Effect Of Streptozotocin Research Articles

The Diabetogenic Effects of Streptozotocin in Mice are Prolonged and Inversely Related to Age

Single "subdiabetogenic" doses of streptozotocin (SZ), when given to young male CD-1 mice, produced a delayed onset of hyperglycemia dependent on the dose of SZ and on the age of the mice. The effect was markedly reduced or absent in older mice given the same dose of SZ per kg of body weight. Histologic examination of the pancreas of these animals revealed that SZ induced greater damage to the islets of the young mice compared with older mice. In addition to the characteristic findings of a decrease in insulin-containing cells and an increase in glucagon- and pancreatic polypeptide-containing cells there was evidence of new islet formation. Delayed-onset hyperglycemia was also induced in young inbred DBA/2J, C57BL/KsJ, and SWR/J mice with single SZ doses as well as with alloxan in young CD-1 mice, indicating that the effect was not specific for CD-1 mice not for SZ as the agent inducing beta-cell injury. The induction of beta-cell autoimmunity did not appear to be important in the delayed diabetogenic effect of SZ, since insulitis was rare and followed the onset of hyperglycemia when seen, and islet cell autoantibodies were not found. Rather, SZ induced more beta-cell destruction in young animals than in older mice, and the continued somatic growth of the former suggests that the delayed hyperglycemia was due to an out-growing of a reduced insulin supply. That mild to severe diabetes could be induced by the same dose of SZ/kg, depending only on the age of the mice when SZ was given, may have implications for understanding the apparent heterogeneity of human diabetes mellitus.

The diabetogenic effects of streptozotocin in mice are prolonged and inversely related to age

The diabetogenic effects of streptozotocin in mice are prolonged and inversely related to age

Adrenergic receptors and the onset of streptozotocin-induced diabetes in mice

Abstract Treatment with yohimbine, an α 2 -adrenergic blocker, prior to the injection of a subdiabetogenic dose of streptozotocin (STZ) produced hyperglycemia and hypoinsulinemia in mice 7 days later. Prazosin, an α 1 -adrenergic blocker, was ineffective. The capacity of phentolamine and phenoxybenzamine to potentiate the diabetogenic effect of STZ was intermediate between that of yohimbine and prazosin. Propranolol and hexamethonium inhibited the potentiating action of yohimbine. Yohimbine enhanced the potentiating effect of isoproterenol on the STZ-induced diabetes. Acute changes in plasma glucose and insulin levels induced by STZ were potentiated by yohimbine but not by prazosin. The insulin releasing ability of the pancreatic islets 7 days after STZ was all but lost in mice pretreated with yohimbine but not with prazosin. These results suggest that the β- and α 2 -, not α 1 -, adrenergic system which modulates insulin release from pancreatic islets influences the response to the diabetogenic action of STZ in mice.

Influence of Age on the Sensitivity of the Rat to Streptozotocin

The relationship between age and sensitivity to the diabetogenic effect of streptozotocin was investigated. Changes in the serum levels of several parameters (glucose, immunoreactive insulin, lipids), as well as changes of the pancreatic insulin content were monitored at 2, 4, 8, 24 and 48 h after the intravenous administration of different doses of streptozotocin in rats of various weights. Different concentrations of blood glucose and lipid and different amounts of pancreatic immunoreactive insulin could be found in rats of different ages 24 and 48 h after injection of the same dose of the drug (in mg/kg body weight). Also, age-dependent changes of serum immunoreactive insulin could be observed as early as 4 h after streptozotocin administration. All these changes indicate that the sensitivity of the rat to the diabetogenic effect of streptozotocin is inversely related to the age of the animals. Most likely, age-dependent pancreatic factors have an important role. In fact, the changes of the minimum dose of streptozotocin required to cause diabetes in rats of different weights closely parallel the age-related changes of the total immunoreactive insulin content of the pancreas of the intact rats. The role of other age-related factors which may influence the effectiveness of streptozotocin action is briefly discussed.

Increased Aryl Hydrocarbon Hydroxylase Activity in Hepatic Microsomes from Streptozotocin-Diabetic Female Rats

In streptozotocin-induced diabetic male rats, hepatic microsomal aryl hydrocarbon hydroxylase (AHH) activity was depressed to less than control values, but was increased in microsomes from diabetic female rats. Insulin treatment of diabetic animals returned the altered AHH activity to control values in both sexes of rats. 2. Hepatic microsomal AHH activity was increased over control values in both sexes of diabetic mice. 3. Protection of female rats from the diabetogenic effects of streptozotocin by nicotinamide pretreatment also prevented the increase in AHH activity observed in unprotected animals. 4. Treatment of control and diabetic female rats with 3-methylcholanthrene resulted in larger increases in hepatic AHH activity in control animals, but similar increases in cytochrome P-448 content occurred in both treatment groups. 5. Differential stimulatory or inhibitory effects on AHH activity were observed after the addition of SKF 525-A, metyrapone, and rotenone to hepatic microsomes in vitro from control and diabetic female rats. However, similar stimulatory responses in AHH activity were observed after addition of alpha-naphthoflavone to microsomes from both treatment groups.

Diabetogenic effect of streptozotocin in the rat during the perinatal period.

The diabetogenic effect of streptozotocin was investigated in the rat during the fetal and neonatal life. Streptozotocin was directly injected in the vitellin vein of the fetus or in the saphenous vein of the neonate. In the 21.5 day old fetus, diabetogenic activity was demonstrated with a single dose of 100 μg/gm. administered the day before, and this was indicated by a fall in the pancreatic insulin content to 20 per cent and a lowering of the plasma insulin to 60 per cent of the controls. A single dose (100 μg/gm.) of streptozotocin administered on the day of birth produced an overt diabetes in the neonate: the maximal fall in the pancreatic insulin content (7 per cent of the controls) was observed four days after the streptozotocin injection, during the highest blood glucose level (300 per cent of the controls). A significant increase in the pancreatic glucagon content was observed twenty-four hours after the maximal insulin depletion. Liver glycogen content was occasionally decreased. More severe diabetes was obtained by two streptozotocin injections (50μg/gm.), with lowest pancreatic and highest blood glucose levels at 1 per cent and 60 per cent, respectively. A clearcut drop of the plasma insulin/glucose ratio was observed in the drug-treated animals. Three weeks after injection(s), basal blood glucose and plasma insulin levels were normal, although impairment of insulin secretion still appeared after glucose load and insulin pancreatic content was still slightly lower. A rapid and spontaneous, if not quite complete recovery, is a characteristic pattern of the streptozotocin diabetes in the neonate as compared to that in the adult.

Streptozotocin diabetes: time course of irreversible B-cell damage; further observations on prevention by nicotinamide.

Further studies on the mode of action of streptozotocin and the prevention of its effects by nicotinamide have yielded the following results: 1. The injection of nicotinamide at varying time intervals after streptozotocin afforded partial protection against its β-cytotoxic effects, decreasing with the length of the intervals but still significant when the interval was 2 hr. 2. Manno-heptulose failed to suppress the insulin release occurring between 6 and 10 hr after the injection of streptozotocin. 3. Nicotinic acid administered by gastric tube failed to protect against the diabetogenic effect of streptozotocin. 4. Nicotinamide injected 10 min after alloxan afforded no protection against the diabetogenic effect of the latter. It is concluded (1) that the β-cytotoxic effect of streptozotocin is not immediately irreversible or that it does not affect all B-cells simultaneously; (2) that the insulin release observed between 6 and 10 hr after the injection of streptozotocin occurs by way of leakage from damaged B-cells; (3) that the ineffectiveness of nicotinic acid in preventing the β-cytotoxic effect of streptozotocin is probably not the consequence of its insufficient conversion to nicotinamide after parenteral administration; and (4) that streptozotocin and alloxan differ in their mechanism of action on the pancreatic B-cell.