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In wild-type mice, a single injection of streptozotocin (STZ, 200 mg/kg body wt) caused within 4 days severe hyperglycemia, hypoinsulinemia, significant glucose intolerance, loss of body weight, and the disappearance of pancreatic beta-cells. However, in ATP-sensitive K(+) channel (K(ATP) channel)-deficient mice (Kir6.2(-/-) mice), STZ had none of these effects. Exposing isolated pancreatic islets to STZ caused severe damage in wild-type but not in Kir6.2(-/-) islets. Following a single injection, plasma STZ levels were slightly less in Kir6.2(-/-) mice than in wild-type mice. Despite the difference in plasma STZ, wild-type and Kir6.2(-/-) liver accumulated the same amount of STZ, whereas Kir6.2(-/-) pancreas accumulated 4.1-fold less STZ than wild-type pancreas. Kir6.2(-/-) isolated pancreatic islets also transported less glucose than wild-type ones. Quantification of glucose transporter 2 (GLUT2) protein content by Western blot using an antibody with an epitope in the extracellular loop showed no significant difference in GLUT2 content between wild-type and Kir6.2(-/-) pancreatic islets. However, visualization by immunofluorescence with the same antibody gave rise to 32% less fluorescence in Kir6.2(-/-) pancreatic islets. The fluorescence intensity using another antibody, with an epitope in the COOH terminus, was 5.6 times less in Kir6.2(-/-) than in wild-type pancreatic islets. We conclude that 1) Kir6.2(-/-) mice are STZ resistant because of a decrease in STZ transport by GLUT2 in pancreatic beta-cells and 2) the decreased transport is due to a downregulation of GLUT2 activity involving an effect at the COOH terminus.

Of four fractions (CH2Cl2, EtOAc, BuOH and H2O) from mustard leaf (Brassica juncea), the EtOAc fraction showed the strongest inhibitory effects, which were concentration-dependent, on the formation of advanced glycation end products and free radical-mediated protein damage in an in vitro system, indicating that this fraction has a potential protective role against diabetes and/or its complications. Based on these results, we carried out an in vivo study to determine whether the EtOAc fraction protected against diabetic oxidative stress induced by streptozotocin. Oral administration of the EtOAc fraction at doses of 50 and 200 mg/kg body weight/d for 10 d reduced the serum levels of glucose and glycosylated protein, implying that the impaired glucose metabolism due to diabetes had been ameliorated. In addition, the EtOAc fraction significantly reduced the thiobarbituric acid-reactive substance levels of serum and hepatic and renal mitochondria. Furthermore, the elevated levels of superoxide and nitrite/nitrate were reduced in a dose-dependent manner by oral administration of the EtOAc fraction. These findings suggest that the EtOAc fraction from mustard leaf might be beneficial in attenuating the damage caused by oxidative stress involved in diabetes and its complications.

The effect of hypertension on the progression of diabetic cardiomyopathy was examined by attempting to induce a similar level of diabetes in both spontaneously hypertensive rats (SHR) and Wistar rats. Streptozotocin (STZ) was injected into SHR (45 mg/kg) and Wistar rats (55 mg/kg) before (eight weeks of age) and after (twelve weeks of age) the development of hypertension in the SHR. For both groups of animals, induction of diabetes resulted in depressed weight gain, increased food and fluid consumption, hypoinsulinemia, hyperglycemia, and hypertriglyceridemia. For the rats injected at eight weeks of age, an oral glucose tolerance test (OGTT) demonstrated that although the SHR were significantly less diabetic than Wistar rats, the degree of cardiac dysfunction was equivalent in both strains. These results suggest that hypertension was interacting with the diabetic condition to impair cardiac performance. Injecting SHR at twelve weeks of age increased the severity of diabetes but interestingly did not depress heart function compared with the non-diabetic SHR group. Injecting Wistar rats at this age also increased the severity of diabetes, but unlike the SHR diabetic animals, these rats still had impaired cardiac performance. These results suggest that hypertension exacerbates the cardiac dysfunction seen during diabetes, especially when SHR rats are injected with STZ prior to the elevation of blood pressure. Moreover, in the SHR, the development of LV hypertrophy at the time of STZ injection may have compensated for the damaging effects of diabetes on the myocardium, thereby enabling the heart to perform normally.

Glucocorticoids and insulin effect long-term reciprocal changes in food intake and body weight. We tested the interactions of corticosterone and insulin on caloric efficiency, white adipose tissue (WAT) stores, and brown adipose tissue (BAT). Two experiments were performed: 1) adrenalectomized rats were treated with corticosterone with or without streptozotocin-induced diabetes and 2) adrenalectomized, corticosterone-treated, diabetic rats were treated with insulin. By 4-5 days later, > or = 50% of the variance in caloric efficiency, plasma triglycerides, and WAT stores was explained by regression of these variables on corticosterone (catabolic) and insulin (anabolic). When the ratio of the hormones was normal, but concentrations high, overall gain of energy stores decreased and energy was redistributed to fat. Both hormones were anabolic on BAT lipid storage; the hormones played a complex role in the regulation of uncoupling protein (UCP) in BAT. Although corticosterone inhibited and insulin stimulated UCP, these effects were only evident in diabetics and with normoglycemia, respectively. For BAT variables, < or = 50% of the variance was explained by regression on corticosterone and insulin, suggesting that the effects of these hormones are mediated through an intermediate such as sympathetic nervous system input to BAT.

The acute administration of some benzodiazepines in normoglycemic rats induced only minor changes of the blood glucose levels. In Triton WR-1339 administered rats, the benzodiazepines brought about minor modifications of this parameter. However, in diabetic rats (streptozotocin-induced diabetes), diazepam administered subacutely elicited very significant diminutions of glycemia. This was due, at least partly, to an increase of the glucose uptake by the skeletal muscle.

Chlorozotocin is a new anticancer agent with the chloroethylnitrosourea cytotoxic moiety attached to the carbon-2 position of glucose. Like other chloroethylnitrosoureas, this agent produces delayed myelotoxicity which is dose-limiting. A phase I trial of chlorozotocin with administration of glucose was done in an attempt to modify the myelotoxicity. The patients received the first course of chlorozotocin (200 mg/m2) in the fasting state and then the second course of chlorozotocin with boluses of a 50% glucose solution. With the second course of chlorozotocin administration, the glucose concentration remained threefold greater than after the first course for at least 1 hour. The plasma half-life and apparent volume of distribution of chlorozotocin were similar following either course. The wbc, neutrophil, and platelet count nadirs after the first course of this agent were not significantly different than the nadirs after the second course. We were unable to modify the myelotoxicity of chlorozotocin with boluses of a 50% glucose solution.

Chlorozotocin was administered by rapid intravenous infusion to 35 patients with advanced cancer on either single-day of five-consecutive-day schedules. Total doses per course ranged from 12.5 to 200 mg/m2. On either administration schedule, dose limiting toxicities were thrombocytopenia and leukopenia at total doses of 150 mg/m2 to 200 mg/m2. Repetitive courses of drug may produce progressive impairment of renal and bone marrow function. Nausea and vomiting were infrequent and mild without definite relationship to dose. Minor reversible nondose related increases in SGOT and in serum creatinine occurred at all doses on both schedules. The plasma half-life of intact N-nitroso groups averaged 9.5 minutes after rapid intravenous administration of doses up to 40 mg/m2 and 12.5 minutes after doses of 150 or 200 mg/m2. No differences between plasma half-lives were seen between identical doses given on the first and fifth days of the five-day schedule. Objective tumor regression was noted in one patient with bronchogenic large cell carcinoma and one patient with metastatic melanoma.

We have studied the effect of a number of nitroimidazole sensitizers of varying lipophilicity on the pharmacokinetics of CCNU in mice. It was found that the effectiveness of these compounds in producing pharmacokinetic effects correlated directly with their lipophilicity, viz. in the order: benznidazole (Benzo) greater than Ro07-1902 misonidazole greater than (MISO) greater than Ro05-9963. The effects of MISO on the pharmacokinetics of 4 nitrosoureas of differing lipophilicity were also investigated. The plasma clearances of CCNU, BCNU and MeCCNU (high lipophilicity) were slowed by MISO whereas that of chlorozotocin (Chlz) (low lipophilicity) was unaffected. Thus, it seems that for a pharmacokinetic interaction to occur between a nitroimidazole and a nitrosourea, both the modifier and the cytotoxic agent must have a requisite degree of lipophilicity. As the same requirement appears to hold for enhancement of tumor response, these data provide further evidence that pharmacokinetic modification plays a major role in chemosensitization.

A mathematical model for streptozocin metabolism in mice is presented. By using the available bioassay and chemical assay data for a 300-mg/kg ip injection and the principles of physiologically based pharmacokinetics, a membrane-limited transport model with first-order kinetics was found to simulate the data adequately (average error of less than 20%). Furthermore, the first-order reaction constant derived in analyzing the bioassay data (0.009 min-1) was in close agreement with the half-life of streptozocin (1 hr) reported previously.

Plasma pharmacokinetics were compared in patients with advanced sarcomas receiving adriamycin, 60 mg/m2 intravenously (iv) on day 1 every 3 wk in combination with streptozotocin, 500 mg/m2/day iv on days 1 to 5 every 3 wk, and patients receiving adriamycin alone in the same dose and schedule. The combination-treated group had greater adriamycin drug exposure (concentration X time) when serial plasma levels were analyzed by fluorescence assay and by radioimmunoassay (RIA). The plasma t 1/2 of adriamycin equivalents measured by fluorescence assay was also significantly prolonged in the combination-treated group. These changes correlated well with an increase in adriamycin-related toxicity--mucositis and myelosuppression-seen in the patients who received the combination drug therapy. Plasma streptozotocin kinetics and the incidence of streptozotocin-related side effects--hepatic and renal function abnormalities--were those published for streptozotocin alone. Evidence is presented to support the hypothesis that the increased incidence of adriamycin side effects is due to streptozotocin-related hepatic dysfunction, affecting both the detoxification and excretion of adriamycin. Combination of other drugs with adriamycin should take into account their potential for inducing hepatic dysfunction which may affect the therapeutic index of adriamycin.

We have investigated the distribution, biotranformation, and excretion of streptozotocin and its 14C- and 3H-labeled metabolities in 15 patients with advanced cancer. Streptozotocin was detected in the plasma during the first 3 hours after administration while radioactive products were present for longer than 24 hours. No unchanged streptozotocin was detected in the cerebrospinal fluid (CSF); however, 14C-labeled metabolites were detected in the 2-hour CSF sample in a concentration equivalent to the 2-hour plasma level. H activity is the CSF was not detected at this time period. Radioactivity measured in biopsied tissues indicated that streptozotocin labeled with 14C and 3H or its metabolites penetrated tumor tissue. 14C tissue levels were found to approximate plasma levels; however, 3H levels were found to be greater than the corresponding plasma levels. Fifteen percent of the total dose of streptozotocin administered was recovered in the urine. 3H-labeled metabolites were recovered in excess of 60% in the urine, and approximately 30% of the 14C-labeled metabolites were recovered in the urine during a similar interval. Less than 1% of the administered 14C and 3H was recovered in the feces. 14C-labeled CO2 was also recovered, although quantitative recovery was not attained. At least three major metabolites of streptozotocin were detected in the urine by radiochromatography. Two metabolites contained only 3H and one metabolite contained both 14C and 3H in the same ratio as administered.