THE STIMULATORY EFFECT OF ENDOTHELIN-1 ON REGENERATING ADRENAL-CORTEXIS REVERSED BY NIFEDIPINE

Endothelin-1 (ET-1), a potent vasoconstrictor, was found to act in non -vascular tissues, for example it enhanced aldosterone output from adr enal zona glomerulosa. As the adrenal cortex is capable of regeneratio n after enucleation, it seemed of interest to study the effects of ET- 1 on adrenocortical regeneration. The study was performed on adult rat s subjected to left adrenal enucleation combined with contralateral ad renalectomy. Mitotic index was employed to assess the proliferation of regenerating adrenal cortex cells. Plasma corticosterone was measured by a standard RIA kit. ET-1 significantly raised the mitotic index of regenerating rat adrenal cortex by six days after surgery. On the oth er hand, nifedipine reduced the proliferation ratio and abolished the stimulatory influence of ET-1. Similarly, ET-1 enhanced corticosterone output from the regenerating adrenal cortex, and this could be preven ted by the addition of nifedipine. This study has shown that ET-1 migh t act as a regulatory factor on the regenerating adrenal cortex via ca lcium channels.