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KMID : 0359319970370020301
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Korean Journal of Veterinary Research
1997 Volume.37 No. 2 p.301 ~ p.310
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Effects of high glucose concentration on IGF-I binding and glucose transporters in renal proximal tubule cells
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Abstract
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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)∼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 $gt; insulin $gt; IGF-II). However IGF-II did not compete for the cultured cell membrane ^(125)I-IGF-I binding site at 10^(-14)∼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-α-D-glucopyranoside(α-MG) uptake was significantly lower(74.41±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 α-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.
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KEYWORD
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