Аннотация:Abstract: Incubation of cultured bovine adrenal medullary cells in Na + ‐free sucrose medium or in Na + ‐free Cs + medium enhanced the synthesis of 14 C‐catecholamines from [ 14 C]tyrosine about two‐ to threefold or sixfold, respectively. The increment of 14 C‐catecholamine synthesis produced by Na + ‐free medium was partially dependent on the presence of Ca 2+ in the medium. Dibutyrylcyclic AMP also stimulated the synthesis of 14 C‐catecholamines in adrenal medullary cells, and the effects of Na + removal and dibutyryl cyclic AMP (5 m M ) on the synthesis were almost additive. The intracellular pH measured by using a weak acid 5, 5‐dimethyloxazolidine‐2, 4‐dione was 7.14 in control cells and when Na + was replaced by sucrose or Cs + , it shifted down to 6.56 or 5.66, respectively. The fall in intracellular pH and the stimulation of 14 C‐catecholamine synthesis were similarly dependent on the concentration of Na + in the medium. The optimal pH of soluble tyrosine hydroxylase was 5.5–6.0 both in control cells and in cells incubated in Na + ‐free med um. These results suggest that removal of extracellular Na + increases the synthesis of catecholamines, at least in part, by shifting the intracellular pH toward the optimal pH of tyrosine hydroxylase.
