The stimulatory effect of endothelin-1 on regenerating adrenal cortex is 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 adrenal zona glomerulosa. As the adrenal cortex is capable of regeneration after enucleation, it seemed of interest to study the effects of ET-1 on adrenocortical regeneration. The study was performed on adult rats subjected to left adrenal enucleation combined with contralateral adrenalectomy. 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 other 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 prevented by the addition of nifedipine. This study has shown that ET-1 might act as a regulatory factor on the regenerating adrenal cortex via calcium channels.