| Objective: The incidence of malignant tumor has been increasing with social development; with the changing of lifestyle and environment, malignant tumor threaten human healthy; while the prevalence of diabetes mellitus has been obviously increasing. Chemotherapy is one of main therapy to cure tumor. Along with the extending of a lot of tumor patients lives , more and more investigations have been done to prevent the side effect of antitumor drugs. Many researchers internal and abroad demonstrated that there were more and more diabetes mellitus during or after chemotherapy, and the carbohydrate tolerance abnormality or diabetes mellitus would be aggravated, so a lot of researchers pointed that antitumor drugs might damage the islets and induce abnormal glucose tolerance or diabetes mellitus. While most of them were retrospective researches, few of them were animal experiment in which the blood glucose and insulin secrection were determined after intravenous or intraperitoneal injection of antitumor drugs. But there were many interference factors, such as the application of adrenal cortex hormone (ACH) and macrophage colony stimulating factor (M-CSF), insulin resistance and so on. At present there are few evidence that antitumor drugs have effect on islet cells which are primarily cultured. Mitomycin (MMC) is one of the antitumor drugs and is used for many kinds of tumorous chemotherapy. Now there have been few studies of animal in vivo which have confirmed that MMC could damage pancreatic islets.In this research, pancreas of Wistar rats were dislodged and digested . Then pancreatic islets were centrifuged and treated with MMC of different concentrations, the effect of the antitumor drugs on insulin secrection and apoptosis of islets were examined.Methods: Twenty-five healthy male Wistar rats (140±10g,age 6 weeks) were adaptabilitily feeded for three days and absoluted for 10 hours. Then under the condition of axenic celiac, rats were anesthetized . Pancreatic islets were isolated from the pancreas by collagenase digestion, In brief, pancreas were procured and wagitately digested at 37℃in water for 20 min. Pancreatic islets were purified by Ficoll 400, then were separated from the remaining exocrine tissue by hand picking under a stereomicroscope. And the islets were randomly divided into different groups. The islet cells were firstly transferred to RPMI1640 supplemented with 10% heat-inactivated fetal bovine serum (10%FBS) and cultured at 37℃for 1h. Then islets were respectively cultured at 37℃for 1h\6h\12h\24hwith MMC of different concentrations.After cultured with different concentrations of MMC, the islets were respectively incubated for 1h in Krebs-Ringer-Buffer-HEPES (KRBH) containing 3mmol/L glucose and KRBH containing 15mmol/L glucose .Then the supernatant of culture solution were collected and stored at -20℃until used, while the islets were collected at -80℃until used.1 Measurements of insulin Radioimmunoassay was used for the determination of insulin concentration.2 Measurements of DNA of the islet cellsCentrifugalization was used to get out DNA . DNA was determined by absorbability of ultraviolet, which was calculated to evaluate the apoptosis of the islet cells. And the measurement of the proportionality between insulin and DNA (insulin/DNA) was calculated to evaluate functional status of the islet cells (insulin secretion).Results:1 Results of weightThere were no significant difference in weight among each group at the beginning of the experiment .(P>0.05).2 Results of DNAAfter the islet cells were cultured for 1h\6h\12h with 3mmol/L (Lo CHO )and 15mmol/L (HG) glucose , in Lo CHO environment, there were no significant difference among all groups (P>0.05); and in HG environment, there were also no significant difference among all groups (P>0.05).After the islet cells were cultured for 24h, in Lo CHO environment, the DNA concentrations of group MMC (0.32mg/mL) were lower than those of groups MMC (0.01mg/mL\0.032mg/mL) and control group(P<0.05), there were no significant difference among other groups (P>0.05);and in HG environment, the DNA concentrations of group MMC (0.32mg/mL) were lower than those of other groups(P<0.05),there were no significant difference among other groups (P>0.05).The islet cells cultured in groups MMC of same concentrations, in Lo CHO environment, there were no significant difference among all groups (P>0.05); and in HG environment, the DNA concentrations of group (cultured in 0.32 mg/mL MMC for 24h) were lower than those of group (cultured for 1h)(P<0.05), there were no significant difference among all groups (P>0.05).3 Results of insulin secretionAfter the islet cells were cultured for 1h\6h, in Lo CHO environment, the insulin secretion of group MMC (0.32mg/mL) were lower than those of other groups(P<0.05), there were no significant difference among other groups (P>0.05); and in HG environment, the insulin secretion of group MMC (0.32 mg/mL) were lower than those of other groups(P<0.05), there were no significant difference among other groups (P>0.05).After the islet cells were cultured for 12h, in Lo CHO environment, the insulin secretion of group MMC (0.32mg/mL) were lower than those of other groups(P<0.05), there were no significant difference among other groups (P>0.05); and in HG environment, the insulin secretion of group MMC (0.32 mg/mL) were lower than those of other groups(P<0.05), the insulin secretion of group MMC (0.1mg/mL) were lower than those of groups MMC (0.01 mg/mL) and control group(P<0.05), there were no significant difference among other groups (P>0.05).After the islet cells were cultured for 24h, in Lo CHO environment, the insulin secretion of group MMC (0.32mg/mL) were lower than those of other groups(P<0.05), insulin secretion of group MMC (0.1mg/mL) were lower than those of groups MMC (0.01mg/mL\0.032mg/mL) and control group, there were no significant difference among other groups (P>0.05); and in HG environment, the insulin secretion of group MMC (0.32mg/mL) were lower than those of other groups(P<0.05), the insulin secretion of group MMC (0.1 mg/mL) were lower than those of groups MMC (0.01mg/mL\0.032mg/mL) and control group ( P < 0.05),there were no significant difference among other groups (P>0.05).The islet cells in groups MMC (0.01mg/mL\0.032mg/mL) and control group, in Lo CHO environment: there were no significant difference among all groups(P>0.05); and in HG environment, there were no significant difference among all groups (P>0.05).The islet cells in group MMC (0.1mg/mL) in Lo CHO environment: there were no significant difference among all groups (P>0.05); and in HG environment, the insulin secretion (cultured for 24h) were lower than those (cultured for 1h)(P<0.05), there were no significant difference among other groups (P>0.05).The islet cells in group MMC (0.32mg/mL) in Lo CHO environment: the insulin secretion (cultured for 24h) were lower than those (cultured for 1h\6h)(P<0.05), there were no significant difference among other groups (P>0.05); and in HG environment, the insulin secretion (cultured for 24h) were lower than those (cultured for 1h\6h\12h)(P<0.05), the insulin secretion (cultured for 12h) were lower than those (cultured for 1h\6h)(P<0.05), the insulin secretion (cultured for 6h) were lower than those (cultured for 1h)(P<0.05).Conclusions:1 In normal environment, there were no significant difference in insulin secretion. The islets were directly impaired by MMC.MMC inhibited insulin secretion.2 After the islets were cultured for a long time , MMC of higher concentration had bad effect on insulin secretion; the glucose stimulated insulin secretion (GSIS) might be earlier impaired. 3 MMC of higher concentration might kill the islet cells...
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