P-6-1 Hydrogenperoxide (H2O2) stimulates tyrosine-phosphorylation of the insulin receptor and its tyrosine kinase activity in intact cells

P-5-14 High Plasma Fasting Level of Pancreatic Polypeptide (PP) in Aged Dogs Pharmacokinetics of PP in Young and Adult Dogs Y. Inoue, Y. Tasaka, K. Marumo, Y. Hirata Diabetes Center, Tokyo Women's Medical College, Tokyo, Japan Fasting plasma PP has been reported to show age-related rise in human subjects. In this study, we found that there were age-related changes of plasma PP in dogs. To elucidate its mechanism pharmacokinetics studies of plasma PP were done in young and adult dogs by single i.v. porcine PP injection, together with that of insulin. For the chron@logical study of plasma fasting PP, IRI and IRG, 70 beagle dogs (2 months to~8 years,-5 months) were investigated. PP, IRI and IRG were measured by RIA. 3 young (6 months to 2 years) and 3 adult (5-18 years) dogs were used for the study of pharmacokinetics of PP and insulin. 1 pg-kg of porcine PP or 0.i U/kg Actrapid insulin was injected i.v. and venous blood sample was taken at -2, -5, 2, 5, i0, 15, 20, and 25 min. The half time of disappearance (t½), the Ke and total clearance of plasma PP and insulin were calculated based on the one-compart model theory. Plasma fasting PP of 2 months to 2-year-old dogs was lower (415 ± 316 pg/ml) than that of 2- to 8-year-old dogs (939 ± 622 pg/ml) (P~O.O02). But no significant age-related changes were found in plasma fasting IRI or IRG in dogs. The t½ of PP in the young (5.8 ± 0.7 min) was similar to that in the adult (6.1 ± i.i min) and the Ke and total clearance values of PP in the young were also similar to those of the adult. Thus we conclude there is also an age-related rise of fasting plasma PP level in dogs and its rise is not due to the delay of PP exertion, suggesting other mechanisms including basal hypersecretion of PP.

P-6-1 HYDROGENPEROXIDE (H20 2) STIMULATES TYROSINE-PHOSPHORYLATION OF THE INSULIN RECEPTOR AND ITS TYROSINE KINASE ACTIVITY IN INTACT CELLS Masato Kasugal, 2, Osamu Koshio I and Yasuo Akanuma 1 iThe Institute for Diabetes Care and Research, Asahi Life Foundation, Tokyo, Japan 2The 3rd Department of Internal Medicine, University of Tokyo, Tokyo, Japan H-35 rat hepatoma cells were labeled with [32p]orthophosphate and their insulin receptors isolated on wheat germ agglutinin (WGA)-agarose and anti-insulin receptor antiserum. The incubation of these cells with i0 mM H202 for lO min increased the phosphorylation of both the serine and tyrosine residues of the B-subunit of the insulin receptor. Next, insulin receptors were purified on WGA-agarose from control and H202-treated H-35 cells and the purified fractions incubated with [y-32p]ATP and Mn 2+. Phosphorylation of the B-subunit of insulin receptors obtained from H202-treated cells was 150% of that of control cells. The kinase activity of the WGA-purified receptor preparation obtained from H202-treated cells, as measured by phosphorylation of src-related synthetic peptide, was increased about 4-fold over control cells. These data suggest that in intact cell systems, H202 may increase the insulin receptor kinase activity by inducing phosphorylation of the B-subunit of insulin receptor.

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