THE ROLE OF NEUROPEPTIDES IN THE REGULATION OF ADRENAL ZONA GLOMERULOSA FUNCTION - EFFECTS OF SUBSTANCE-P, NEUROPEPTIDE-Y, NEUROTENSIN, MET-ENKEPHALIN, LEU-ENKEPHALIN AND CORTICOTROPIN-RELEASING HORMONE ON ALDOSTERONE SECRETION IN THE INTACT PERFUSED RAT ADRENAL

A range of neuropeptides has been identified in the adrenal glands of many mammalian species. In many cases these peptides have been located in nerves supplying the adrenal cortical cells, or within clusters of chromaffin cells within the zona glomerulosa. The function of these neuropeptides has yet to be determined, but from their location within the gland it is clearly possible that they may have a role in the regulation of aldosterone secretion. The effects of Met-enkephalin, Leu-enkephalin, neuropeptide Y, substance P, corticotrophin-releasing hormone (CRH) and neurotensin on aldosterone secretion were investigated using the intact perfused rat adrenal gland in Situ. All the peptides tested, except CRH, caused a significant increase in aldosterone secretion over the dose range of 1 pmol to 10nmol, with a maximum response of about a twofold increase in secretion. Met-enkephalin, however, at a dose of 10 nmol caused a 350% increase in aldosterone secretion, a response comparable with that seen in response to angiotensin II in this preparation. These results suggest that, while substance P, neuropeptide Y, neurotensin and Leu-enkephalin all have the capacity to cause modest increases in the rate of steroid secretion by the zona glomerulosa, these neuropeptides probably do not have a major role in the acute regulation of aldosterone secretion, at least under basal conditions. Met-enkephalin, on the other hand, was a more potent stimulus to aldosterone secretion, and thus may have a role in the control of aldosterone secretion.