[Effect of intracellular administration of L-tyrosine and L-phenylalanine on voltage dependent calcium current in PC 12 pheochromocytoma cells].

Changes in the high-threshold calcium current (Ica) induced by intracellular administration of L-tyrosine and L-phenylalanine have been studied on internally perfused PC 12 pheochromocytoma cells using whole-cell voltage-clamp technique. L-tyrosine (20 microM/l) not only prevented a decay of Ica occurring during intracellular perfusion but induced also its transient recovery. In contrast, L-phenylalanine (20 microM/l) accelerated a decline of Ica. Replacement of ATP in the perfusing solution by an equivalent amount of ADP (2 mmol/l) did not alter the effect of amino acids. alpha-methyl-D, L-tyrosine (a specific blocker of tyrosine hydroxylase) caused the effect similar to that of L-tyrosine.