Effects of high glucose concentration on IGF-I binding and glucose transporters in renal proximal tubule cells

Han, Ho-jae; Park, Kwon-moo; Son, Chang-ho; Yoon, Yong-dal

Korean Journal of Veterinary Research 1997;37(2):301-310.

Ho-jae Han¹, Kwon-moo Park¹, Chang-ho Son¹, Yong-dal Yoon²

¹College of Veterinary Medicine, Chonnam National University
²College of Natural Science, Hanyang University, Hormone Research Center

신장 근위세뇨관세포에서 고포도당이 IGF-I 결합과 포도당운반계에 미치는 영향

한호재¹, 박권무¹, 손창호¹, 윤용달²

¹전남대학교 수의과대학
²한양대학교 자연과학대학, 호르몬연구센터

Abstract

Diabetes mellitus is associated with a wide range of pathophysiological in the kidney. This study was designed to examine the effects of high glucose concentration on IGF-I binding and glucose transporters in renal proximal tubule cells. The results were as follows : The binding of $^{125}I-IGF-I$ reached the peak at the 30 minutes and gradually decreased by the time dependent manner. The binding of $^{125}I-IGF-I$ was inhibited by the unlabelled IGF-I($10^{-14}{sim}10^{-8}M$) in a concentration dependent manner. The relative affinity of IGF-I receptor for IGF-I, IGF-II and insulin exhibited typical type 1 binding(IGF-I > insulin > IGF-II). However IGF-II did not compete for the cultured cell membrane $^{125}I-IGF-I$ binding site at $10^{-14}{sim}10^{-8}M$. Under optimal conditions, IGF-I binding to the membranes from 5mM and 20mM glucose treated cells was analyzed. It was found that 20mM glucose treated cells exhibited higher binding activity for IGF-I. In order to further substantiate this increase in IGF-I binding sites, we performed affinity-labelling studies. The cross-linked cell membrane subjected to SDS-PAGE; labelled material was detected by autoradiography. 20mM glucose treated cells exhibited higher levels. The initial rate of $methyl-{alpha}-D-glucopyranoside({alpha}-MG)$ uptake was significantly lower($74.41{pm}6.71%$) in monolayers treated with 20mM glucose than those of 5mM glucose. However, 3-O-methyl-D-glucose(3-O-MG) uptake was not affected by glucose concentration in culture media. IGF-I significantly increased ${alpha}-MG$ uptake in both 5mM and 20mM glucose treated cells. However, 3-O-MG uptake was not affected by IGF-I in both conditions. In conclusion, 20mM glucose increased binding sites of $^{125}I-IGF-I$, inhibited Na/glucose cotransporter activity. But 20mM glucose did not change facilitated glucose transporter.

Key Words: Glucose, IGF-I, Transporter, Kidney