Metabolic effects of streptozotocin-induced diabetes in ovarectomized rats

Little information is available about how the changes that occur around the time of menopause might affect management of diabetes mellitus .The present study investigates the metabolic consequences of estrogen deficiency with streptozotocin induced-diabetes. The study was performed on 130 female Wistar rats, allocated into 4 groups: control [Sham]; diabetic [STZ]; ovarectomized [OVX] and ovarectomized diabetic [OVX-STZ] .Rats were subjected to determination of body weight and body mass index [BMI]. Estimation of blood glucose, plasma levels of insulin, estradiol, leptin, malondialdehyde, lipids, atherogenic index as well as in vitro diaphragmatic glucose uptake and renal glucose output. OVX- STZ rats showed significantly lower body weight and BMI than OVX rats. Blood glucose level was significantly higher than Sham, STZ and OVX groups. Diaphragmatic glucose uptake significantly decreased, while renal glucose output significantly increased compared to OVX and Sham groups .Plasma lipid profile in OVX-STZ rats was worse than Sham, STZ and OVX groups as indicated by the significant increase in plasma triglycerides, total plasma cholesterol and LDL-c. Atherogenic index was significantly higher than Sham and OVX rats. Similarly, lipid peroxidation was significantly higher than Sham, STZ and OVX groups. Plasma insulin decreased significantly compared to Sham, STZ and OVX groups, while the decrease in plasma leptin was significant when compared to Sham group. The present study demonstrates that metabolic derangements of combined insulin and estrogen deficiency overweigh the derangement of either hormone deficiency in postmenopausal period

Physiological studies on the protective effect of melatonin against doxorubicin cardiotoxicity

This study was designed to investigate the effect of melatonin pretreatment on doxorubicin-induced cardiotoxicity, using Langendorff model of isolated perfused rat hearts. Male Wistar rats were divided into 2 groups, the first was untreated served as the control group and the second was melatonin pretreated test group. Rats of the test group received melatonin in a dose of 5mg/kg body weight, one hour before heart isolation. Hearts isolated, from both groups, were perfused with 30 micro M doxorubicin [DXO] for 60 minutes. The cardiac functions were assessed at 10, 30 and 60 minutes by heart rate [HR], peak tension [PT], time to peak tension [TPT], half relaxation time [HRT], and myocardial flow rate [MFR]. Cardiac muscle samples were ultrastructurally examined by electron microscope. DXO perfusion induced marked deterioration in cardiac functions of the control rats. At 60 minutes of DXO perfusion, there were significant bradycardia, significant increase in PT and significant prolongation in all cardiac times. Moreover, MFR was significantly compromised during the whole period of DXO perfusion. Ultrastructural examination revealed myofilament disarray with areas of focal loss and necrosis, hyper-contracted fibers and rarefied mitochondrial matrix, signifying its degeneration. Melatonin pretreated hearts, at 60 minutes of DXO perfusion, had significantly less bradycardiac response, significantly enhanced TPT and HRT, as well as a significantly higher MFR compared to the untreated control group. Therefore, the observed DXO-induced deterioration in cardiac chronotropy, inotropy, lusitropy and myocardial flow, was greatly attenuated by melatonin pretreatment. Moreover, melatonin could protect the myofilaments from degeneration and preserve mitochondrial integrity. Single injection of melatonin greatly attenuated both structural and functional insults of doxorubicin on the heart. Therefore, melatonin could be recommended as a protective measure against the high risks of doxorubicin-induced cardiotoxicity

Studies on the effects of chromium supplementation on the metabolic response to exercise

Chromium is one of the essential dietary trace elements that an important role in regulating whole body metabolism and energy utilization. However, there is a strong argument about chromium supplementation during exercise training programs, as some authors recommend it and others consider it illegal. Therefore, this work was planned to assess the metabolic responses to exercise training program in conjunction with chromium supplementation. Four rat groups were studied; rats subjected to swim exercise 2 hours/day for 2 weeks, rats supplemented with chromium picolinate in a dose of 90 micro g/kg body weight/day by gavage for 2 weeks and rats exposed to both regimens as well as their control non-exercised non-supplemented rats. Results of the present study revealed improvement in glucose tolerance with insignificant changes in serum insulin concentrations and a remarkable hypolipidemic responses in the three studied rat groups compared to the control. Unexpectedly the metabolic responses of the combination of chromium and exercise training did not exceed those obtained either chromium supplementation alone or exercise alone. Such non-additive effect could be ascribed to the common pathway shared by both chromium and exercise to exert their actions; and either chromium or exercise could, on its own, achieve the maximal response that cannot be further increased by their combination. The beneficial effects of chromium supplementation on increasing insulin sensitivity and improving blood lipid profile makes it an effective agent in treating non-insulin dependent diabetes and arteriosclerosis. Also, chromium has favorable effects in sparing protein use during exercise, decreasing lactate production with conservation of high glycogen content that enables prolongation of strenuous muscular exercise and much delaying the exhaustion point. In conclusion, it is evident from this study that chromium is instrumental in mediating metabolic effects of exercise and its role, in this respect, is physiological not pharmacological. Therefore, it is wrong to deal with chromium as one of the ergogenic substances that considered illegal to use with exercise

Rat's uterine motility responses to calcitonin in vivo

The effect of systemic administration of calcitonin hormone on the uterine contractions is uncertain. This work was carried out to elucidate the in vivo effect of calcitonin hormone administration on the myometrial contractility under different ovarian hormonal influences. All the studied rats were bilaterally ovariectomized and were allocated in 3 categories; estrogen-dominated model, progesterone-dominated model and ovariectomized rat model without any hormonal replacement therapy. Calcitonin hormone was injected intramuscularly in a dose of 1 I.U./kg b.w. for 5 days. The uterine horn preparations isolated from calcitonin-treated rats and their matching controls, were studied in thermostatically adjusted 36 C, isolated organ bath, under basal condition and in response to oxytocin hormone. Systemic administration of calcitonin resulted in a significant prolongation of the average relaxation time, average duration of contraction and a decrease in the total serum calcium level, together with an increase in the basal uterine motility index in the different calcitonin-treated rat group compared to their matching controls. This increase in the basal uterine motility could be attributed to its hypocalcemic effect. The effect of calcitonin hormone treatment on the basal uterine motility was more obvious in progesterone-dominated medium and was nullified in the estrogendominated enviroment, demonstrating the potentiating effect of progesterone and the antagonizing effect of estrogen on the calcitonin actions on the myometrial contractility. Regarding the uterine responses to oxytocin, systemic administration of calcitonin hormone completely abolished the uterine motility responsiveness to oxytocin that was clearly observed in estrogen-dominated media, demonstrating its inhibitory effect on the uterine smooth muscles. The calcitonin- induced myometrial relaxation was clearly obvious in all the studied rat models and this may point to its great value, when induction of uterine quiescence is needed, such as in treatment of threatened abortion or in increasing the success rate of in vitro fertilization [IVF]

Age related changes of intestinal motility in rats

The pattern of intestinal motility in different segments of the small and large intestine as well as plasma VIP level were studied in young, adult, old and senescent male albino rats. Results obtained in this study showed that aging has a suppressive effect on the different intestinal motility parameters and this intestinal motility dysfunction was more manifest in the senescent rats than in the old ones. The frequency of contractions of the duodenum and descending colon was significantly reduced with marked prolongation in the average duration of contractions in old and senescent rats compared to the young rats. Regarding the motility index in the duodenum, ileum and descending colon, it was reduced in old and senescent rats compared to the adults. This decrease was more pronounced and statistically significant in the senescent group. There was. Insignificant decrease in the plasma VIP levels with the advance of age and it was not related to the dysmotility of aging. Intramuscular injection of vitamin E for two successive months significantly increased the average force of contraction and motility index of both the small and large intestinal regions especially the caecum and descending colon. This improvement was more evident in senescent than old rats