Effects of insulin on glucose transporters and metabolic patterns in Harding-Passey melanoma cells.

The effect of insulin on glucose metabolism through different pathways and the glucose transporters in Harding-Passey melanoma cells have been studied. Glucose was utilized at a rate of 6.9 +/- 2.3 (SD) mumol X g-1 X h-1 with 86% transformed into lactate and pyruvate and only 0.43 and 3% metabolized through the tricarboxylic acid cycle and the pentose phosphate pathway, respectively. Of the total glucose consumed 2% was used in protein synthesis and 2% was used for lipid synthesis. Hexokinase isoenzyme was type I and enolase was present mainly in the alpha gamma hybrid form. The glucose transporters were cytochalasin B sensitive. The number of high affinity cytochalasin B binding sites was 175,000 receptors/cell (about 0.6 pmol/mg protein) and Kd = 1 X 10(-7) M. Insulin increased glucose utilization and lactate production by about 70% and caused a 56% increase in transport without alterations in the Kd of the site. Insulin receptors were quantified by binding assay using 125I-insulin. Kd was 11 X 10(-9) M with the number of receptors calculated as 11,500/cell. Harding-Passey melanoma cells could thus be a useful model to study basic metabolic events and their modulation by hormones or other effectors.