부산대학교 도서관

The purpose of these experiments was to determine the relative content and biosynthetic rate of insulins I and II under various experimental conditions. The two insulins were quantitated by polyacrylamide gel electrophoresis, electrotransfer to nitrocellulose paper, photoaffinity crosslinking, and immunodetection with anti-insulin antibody and 125 I-labeled protein A. The ratio (mean ± SEM) of insulins, I/II, was 1.2± 0.2 in Wistar-Furth rats fasted for 4 days, 1.6± 0.2 in normal rats, and 5.5± 0.8 in growth hormone-tumor-bearing hyperinsulinemic rats (P < 0.01). The increase in content of rat insulin I compared to II in the growth hormone-tumor-bearing animals was confirmed by radioimmunoassay of gel slices. To determine whether the difference in contents of rat insulins I and II in the hyperinsulinemic rats was due to increased biosynthesis or a different turnover rate, isolated rat islets were incubated in [ 3 H]leucine for 4 hr with 5.5 mM or 16.0 mM glucose in the incubation medium. Glucose stimulated insulin biosynthesis >8-fold. The ratio of synthesis of rat insulin I relative to II was 0.9± 0.1 at 5.5 mM glucose and 9.8± 3.3 (P