Adrenal renin: regulation and function.

Extrarenal renin has been identified in a variety of tissues. All of the components of the renin-angiotensin system have been detected in some organs, including the adrenal gland. A number of hypotheses have been expressed regarding the physiological function of these extrarenal renin systems, but no specific function has been clearly identified. This review focuses on the renin system in the adrenal cortex. Renin has been found in a variety of species, including the human adrenal cortex and adrenal tumors. Our investigations have focused on the renin-angiotensin system in the adrenal cortex of the rat, and have shown that renin is mainly present and synthesized in the zona glomerulosa cells. Renin production is under physiological control and can be altered by changes in electrolyte intake, adrenocorticotrophic hormone (ACTH), and the genetic background of the rat. In these experiments, a positive correlation between adrenal renin and aldosterone concentration is found. Furthermore, in primary culture of zona glomerulosa cells, a converting enzyme inhibitor can reduce the aldosterone stimulation by ACTH and potassium. However, these studies by themselves are not convincing evidence of the physiological role of the adrenal renin system. Further investigations are necessary to determine its role, if any, in adrenal function.