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Effects of Insulin on Glucose Transporters and Metabolic Patterns in Harding-Passey Melanoma Cells¹

Departmento de Bioquimica, Facultad de Biologia, Universidad de Murcia, 30001 Murcia, Spain

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) µmol 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 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 K_d = 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 K_d of the site.

Insulin receptors were quantified by binding assay using ¹²⁵I-insulin. K_d 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.

¹ This investigation was supported by Research Grant CAICYT 2529/83 from the Spanish Ministry of Education and Science.

² To whom requests for reprints should be addressed, at Departamento de Bioquimica, Facultad de Biologia, Universidad de Murcia, 30001 Murcia, Spain.

Received 11/14/85. Revised 2/28/86. Accepted 4/18/86.