| Objective:For the past few years ,the morbility of tumor raised obviously,the morbility of malignant tumor is raising too,especially the lung cancer.By the year of 2015,the number of tumor patients all over the world will reach 15 million,people who die of tumor will be 9 million.At the same time,chemotherapy as a adjuvant or chief therapeutic method of malignant tumor is used widespread.As a result , more and more patients receive chemotherapy.people are paying more and more attention to the side effects of chemotherapy.Recently,there have been some clinical reports on impaired glucose tolerance, or diabetes mellitus induced by chemotherapy.But by now,most of the researches are restricted at retrospective analysis.It is important to study the influence of chemotherapy on blood glucose,insulin secretion and tissue-structure.Mitomycin(MMC)is one of the antibiotic antitumor drugs.In its chemical constitution,there are ethylene-imine and carboxamide group.They have alkanisation.These groups can inhibit duplication of DNA by cross-linking with double strands of DNA.They also break part of DNA. MMC that has a wide anti-tumor spectra is no cycle specific drug.Its t1/2 is one hour.The main adverse effects are obvious and lasting marrow depression and gastrointestinal tract reaction.Sometimes it causes mesenchymal pneumonia.It is reported that the survival time of transplanted rat pancreatic islets can be prolonged when being incubated with MMC in proper concentration.But the function of transplanted rat pancreatic islets would be depressed if the concentration is higher.By now,there is no vivo reports of effects of MMC on blood glucose and function of pancreatic islets.In our research we administered a proper dose of MMC to rat by vein.We studied the effect of MMC on blood glucose,insulin secretion of pancreatic islete and histomorphology of pancreas and liver.Methods: Healthy Wistar rats(n=34),male,six-weeks old.The 34 rats were randomized to two groups,14 in control group(C group),20 in test group(T group).They were kept in an airconditioned room(22±2℃,55%~65% relative humidity)with artifiticial lighting room from 06:00 to 18:00.They were kept individually.They were fed with standard laboratory chow diet which consisting 60% carbohydrates,11% fat,29%protein in calories.After one week's of accomodation,we gave salin to the rats in control group through tail vein, and MMC to rats in test group.All the dose was according to the dose calculation method of animals from experimental zoology,the human's routine dose was 10mg each time by abdominal injection,the rat was ten times of human's. The formulation was 10mg÷60Kg×10(mg/Kg body of rat).The second day after administration (48 hours later),we did intraperitoneal glucose tolerance test (IPGTT).The rats those were killed the third day after admistration,the pancreas and livers were conserved for light microscope and electron microscope detection.Before killing ,blood were collected to examine hepatic function.All rats were bred standard laboratory chow diet,the daily calorie intake was 60kcal per rat throughout the experiment.The food was replenished daily at 16:00and any food remaining at 10:00 of next day was withdraw at this time.Water was unlimited.All rats were weighed after buying, before giving treatment and IPGTT.All rats fasted for 10 hours (from 06:00 to 16:00 of the same day)before doing IPGTT. The next day after IPGTT end the experiment,and pancreas and livers were taken,some for light microscope was stored in 4% neutral formalin solution,some for electron microscope was stored in 4% glutaral.Before killed,blood was collected from the angula vein and serum for hepatic function measurement were separated and stored at -20℃.1 The measurements of blood levels of glucose and insulinGlucose oxidase method was used for the determination of glucose and radioimmunoassay for the the determination of insulin levels.Homeostasis Model Assessment (HOMA-IR) and insulin sensitivity index (ISI) were calculated to evaluate the resistance and sensitivity of insulin.FINS:fasted insulin. HOMA-IR=(FBG×FINS)/22.5; ISI=1/(FBG×FINS), and they were expressed by natural logarithm.2 The measurement of liver function ALT,AST andγ-GT were measured according to the method of IFCC.3 The intraperitoneal glucose tolerance test (IPGTT)All rats were subjected to an IPGTT before ending the experiment.The steps were as follows: All rats fasted for 10 hours (from 06:00 to 16:00 of the same day).Around 16:00,fasting blood was collected from the tail vein,then rats were administered 20% glucose solution intraperitoneally,the dose was 2.0g/Kg glucose.Then blood was collected from the tail vein at 20 min,60min,120min after glucose loading.The plasma was separated immediately for different using.4 The morphological examination of pancreatic and liver tissueThe tissue section was made by routine method,colored by HE.The tissue section for electron microscope was made followed the standard strictly.5 Statistical methodsAll data were treated with SPSS13.0,data presented as mean±SD( X±S).The statistic significance was determined by T-test between groups.The significance was indicated by P-value.The significant difference which had the significance was indicated by P<0.05.Results:1 The effects on the weight of ratsAt the beginning,the rats were randomized,weight of normal control group was (140.43±5.62g),that of test group was (140.17±7.55g), P>0.05,there was no significant difference.Before giving treatment and IPGTT, weight of control group was (181.29±28.70g) and (189.14±17.54g),that of test group was (181.67±18.53g )and (184.09±14.57g), P>0.05,there was no significant difference.2 Plasma glucose concentrations during IPGTTThe fast blood glucose(FBG)of control group was (6.47±0.64mmol/L),that of test group was (6.60±1.37mmol/L), P>0.05, there was no significant difference.The blood glucose level of 20min (13.14±3.78mmol/L) was much higher than that of normal control group(9.83±1.71mmol/L,P<0.05;The blood glucose level of 60min(8.78±1.44mmol/L) was higher than that of control group(7.42±1.03mmol/L) ,P<0.05;The blood glucose level of 120 minute (7.35±1.26mmol/L) was much higher than that of control group(5.57±0.80mmol/L), P<0.01.3 Insulin concentrations during IPGTTThe fasting plasma insulin(FBIN)concentration in control was(11.82±1.59 mIU/L),and plasma insulin reach the peak(45.94±10.58 mIU/L)20 minutes after intraperitoneal injection of glucose,which was about 3.89 times of FBIN.The FBIN of test group was (11.75±0.88mIU/L),there was no significant difference compared with control group,P>0.05.The peak of test group ( 30.54±3.55mIU/L ) was also at 20min after intraperitoneal injection of glucose, which was about 2.60 times of FBIN,and was lower than that of control group(P<0.01). And the plasma insulin level of test group in 60min(21.25±3.17 mIU/L)was lower than that of control group(25.80±3.93 mIU/L, P<0.05). there was no significant difference in 120min insulin concentrations between these two groups, P=0.05.4 HOMA-IR,ISI during IPGTTCompared with control group,there was no significant difference in HOMA-IR and ISI, P>0.05.5 The effect on hepatic functionThere was no siginicant difference in rats'hepatic function between two groups.6 The area under the curve(AUC) of glucose after IPGTTThe AUC of test group between 0~120min was (1120.20±220.88),which was much higher than that of control group(897.53±102.21),P<0.01.7 The AUC of insulin after IPGTTThe AUC of test group between 0~120min was(2428.5±266.2)which was much lower than that of control group(3186.4±466.3),P<0.01.8 The changes of morphology under light microscope of pancreasThe rats'pancreatic acinar cells were lightly swelled in test group,which were the early changes of cells after minor injury.The grains in test group rats'pancreatic isletes reduced.9 The changes of morphology under light microscope of liver tissueIn test group, rats'vacuolar degenerated in hepatic cells,congestion and expansion of sinus hepaticus.10 The changes of morphology under electron microscope of pancreasIn test group,part or most part of crista and membrance of the rats'pancreatic isletes cells were fused,unclear or absent.The rough endoplasmic reticulum was light degranulation.11 The changes of morphology under electron microscope of hepatic tissueIn test group,we can see obvious oedema in rats'hepatic cells,the cellular organs reduced,most part of cristae and part of membrane of mitochondria were fused,unclear.There was obvious degranulation in rough endoplasmic reticulum.Conclusion:1 48 hours after giving mitomycin by vein,blood glucose modulation of rats was abnormal.All of the plasma glucose concentrations of 20min,60min,120min after intraperitoneal glucose tolerance test increased.2 48 hours after giving mitomycin by vein,insulin secretion of rats decreased,the reaction ability after glucose stimulation descended.The plasma insulin concentrations of 20min,60min after intraperitoneal glucose tolerance test were lower than those of normal control group.3 72 hours after giving mitomycin,the morphology of rats'pancreas and livers showed changes of destructiveness and toxicity.Under light microscope,we can see lightly swelled of pancreatic acinar cell,which was the early changes of cells after minor injury.Grains in pancreatic isletes decreased.We can see vacuolar degeneration of hepatocytes,congetion and expansion of sinus hepaticus.Under electron microscope,in rats'pancreatic isletes cells of test group we can see that part or most part of cristae,membrane were fused,unclear or absent,and light degranulation in rough endoplasmic reticulum.About hepatic tissues of test group,we can see obvious oedema,decrease of cellular organ;most of cristae and part of membrane were fused,unclear;there was obvious degranulation in rough endoplasmic reticulum.
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