P-glycoprotein regulating biphasic insulin secretion in rat pancreatic beta cells

Background A 65-kD mdrl （multi-drug resistance protein 1, P-glycoprotein）-Iike protein has been suggested to be the regulatory protein to the chloride channel protein 3 （CIC-3） mediating insulin granules acidification and release in mouse pancreatic beta cells. But the protein has not been deeply investigated. In this study, we identified existence of the 65-kda protein in rat islets and preliminarily explored its biological functions. Methods Total RNAs of rat kidneys served as positive controls, and pancreas, islets and INS-1 cells were extracted for reverse-transcript PCR （RT-PCR）, respectively. The cDNAs were run with specific primers selected from the mRNA of abcblb encoding P-glycoprotein. All PCR products were visualized in agarose gel electrophoresis and sequenced. Homogenates of rat islets and INS-1 cells were applied to SDS-PAGE. P-glycoprotein was detected by a specific monoclonal antibody, C219. Biphasic insulin release was measured in static incubations of rat islets with radioimmunology assay. Results Compared with positive control, expression of the P-glycoprotein mRNA segments were detected in the islets, INS-1 cells and pancreas. Sequence analysis confirmed that the PCR products were matched with mRNA of P-glycoprotein. A 65-kda protein was recognized by the antibody in the islets homogenate but not in that of INS-1 cells in Western-blotting. Instead, the homogenate of INS-1 cells contained a 160-kda protein recognized by the antibody. Insulin secretion of rat islets were stimulated by high glucose （16.7mmol/L）, and showed biphasic curve during 60-minute incubation. After co-incubation with cyclosporine A （CsA）, specific inhibitor to P-glycoprotein, the second phase of insulin secretion was reduced significantly while the first phase was not influenced. Conclusions The 65-kda protein expressed in rat islets is most likely a mini-P-glycoprotein. It may play a key role regulating biphasic insulin release.

Molecular mechanism of limbs＇ postischemic revascularization improved by perindopril in diabetic rats

Background Currently, there are still divergent opinions about the mechanisms of the impaired neovascularization in diabetic subjects. Due to the remarkable therapeutic effect of angiotensin-converting enzyme inhibititors （ACEIs） on the reduction of blood pressure and the protection of target organs, the clinical application of this kind of drugs is very widespread. However, it is still not clear about the role and related molecular pathway of this kind of drugs in the limbs＇ postischemic revascularization. It is of major therapeutic importance to resolve these questions. This study aimed to investigate the reasons of the impaired angiogenesis in the hind limbs of rats with diabetic ischemia, the role and related molecular mechanisms of ACEI in postischemic revascularization. Methods Hind limbs ischemia was induced in diabetic rats by right femoral artery excision. Diabetic rats were randomly allocated to one of the following treatments for 4 weeks： ACEI by perindopril; perindopril in combination with a nitric oxide synthase （NOS） inhibitor; perindopril in combination with bradykinin （BK）-B1 receptor （BIR） antagonist or saline. The differences of angiogenesis, the mRNA and protein expression of endothelial nitric oxide synthase （eNOS）, vascular endothelial growth factor （VEGF） and basic fibroblast （bFGF）, constitutive nitric oxide synthase （cNOS） activity and nitric oxide （NO） content were observed after treatment. Results In non-ischemic hind limbs, no significant changes in capillary density, or the mRNA and protein expression of eNOS, VEGF and bFGF, or the NO content and the cNOS activity were observed among all groups. On the contrary, in ischemic hind limbs, the capillary density in diabetic rats decreased by 27% when compared with the control rats, so did the mRNA and protein expression of eNOS, VEGF and bFGF, or the NO content and the cNOS activity （P 〈0.05）. The capillary density was increased by 1.65-fold in the perindopril treatment group in reference to untreared diabetic rats. Moreover, administration of perindopril enhanced the mRNA expression of eNOS, VEGF, and bFGF by 1.45-, 1.44-, and 1.33-fold, increased the protein content of the above indices by 1.55-, 1.30- and 1.50-fold compared with the untreated diabetic rats respectively. Perindopril also increased NO content and cNOS activity to 1.33- and 1.38-fold of that in untreated diabetic rats. The combination of BK-B1R antagonist significantly decreased the above indices （P 〈0.05）. In contrast, the combination of NOS inhibitor decreased the expression of eNOS and bFGF, the NO content and the cNOS activity, while the expression of VEGF did not change. Conclusions Diabetes mellitus reduces the neovascularization, related growth factors expression and activity in the diabetic rat ischemic legs model. Treatment of perindopril improves postischemic revascularization. This effect is mediated, at least in part, by the BK-B1R-related pathway, and the activation of VEGF/eNOS/bFGF signals may be involved in the pro-angiogenic effect.

Effects of intrauterine exposure to thyroid dysfunction on the development of brain neurons in neonatal rats

Objective To investigate the expression of MCT8,DCX,SHH and ARC /ARG3. 1 in brain neurons of neonatalrats exposed to thyroid dysfunction in uterus.Methods Wistar pregnant rats were randomly divided intocontrol group and experimental groups in which rats weredrunk water with 1, 3, or 5 ppm propylthiouracil(PTU). The thyroid function and morphological changesof PND1 and PND7 were detected. The expression ofMCT8,DCX,SHH,ARC /ARG3. 1 protein in cerebralcortex and hippocampus were detected by Western blot orimmunohistochemistry. Results (1) The levels of TT4decreased significantly in PND1 pups of PTU 3 ppm and5 ppm groups (P < 0. 05 or P < 0. 01). The TSH levelssignificantly increased while FT4 levels significantly decreasedin pups of PTU 5 ppm group on PND7 ( P <0. 05).

Effects of iodine and iron comitant deficiency on thyroid function of rat

Objective To explore the effect of iodine and iron comitant deficiency on thyroid function of rat,and to provide new clues and ideas for prevention and control of iodine deficiency disorders in iron deficiency areas.Methods Using 2×2 factorial analysis method,sixty