Effect of vinblastine on the insulin-receptor interaction in mammalian heart muscle

Isolated muscle cells from adult rat heart were used to investigate the effect of microtubule modifiers on the insulin-receptor interaction in mammalian heart muscle. Preincubation of freshly isolated cells with increasing concentrations of vinblastine resulted in a dose-related inhibition of specific binding of ¹²⁵I-labelled insulin, whereas colchicine did not affect the binding reaction. Analysis of equilibrium binding data demonstrated a reduction of receptor number after treatment of cells with vinblastine. The dissociable fraction of ¹²⁵I-labelled insulin specifically bound at equilibrium was significantly reduced by preincubation with vinblastine. The results suggest involvement of microtubules in the insulin-receptor interaction in cardiac muscle.