Action of insulin on the transport of 3-O-methylglucose in frog sartorius muscles.
The initial rate of entry of 3-O-methyl-D-glucose into isolated frog sartorius muscles was measured at various concentrations of substrate, at 0, 9, 19, or 29 degrees C, after prior incubation at 19 degrees C with a maximally stimulating concentration of insulin. Control muscles were treated similarly, except for the omission of insulin. A saturable transport system provided for most of the entry of 3-O-methylglucose into muscle cells, but a small amount of penetration occurred by a nonsaturable route. The major effect of insulin was to produce a large increase in activity of the suturable system. The Vmax of entry increased, but there was no significant change in the apparent Km. The ratio of insulin-stimulated to basal Vmax was 10 when transport was measured at 29 degrees C but was 22 at 0 degrees C. These findings support the hypothesis that, although a large part of the effect of insulin on sugar transport can be accounted for by an increase in the number of functional transporters in the plasma membrane, there is a separate hormonal effect that permits a relatively greater activity of transporters at lower temperatures, compared with control rates. An additional effect of insulin was to produce a small but definite increase in the entry of sugar by the nonsaturable transport system.
D019325:3-O-Methylglucose; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D005260:Female; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D008757:Methylglucosides / Q000378:metabolism*; D008759:Methylglycosides / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism*; D011894:Rana pipiens; D013816:Thermodynamics
D007328:Insulin; D008757:Methylglucosides; D008759:Methylglycosides; D019325:3-O-Methylglucose