Renin-angiotensin system.

Renin, a protease that cleaves the prohormone angiotensinogen thereby releasing angiotensin I, plays a major role in regulating blood pressure and electrolyte balance. Although renin is synthesized mainly in the cortical cells of the kidney, the presence of renin or reninlike activity has been recognized in various extrarenal tissues of humans and animals, including such reproductive organs as LH-containing cells of the anterior pituitary, placentral trophoblasts, and Leydig cells of the male gonad. It has also been learned that the renin in these extrarenal tissues generates angiotensins locally, which may interact with angiotensin II receptors in a paracrine or autocrine manner. However, the precise roles of the renin-angiotensin system in extrarenal tissue are not yet understood. We demonstrated the renin-angiotensin system in human testis by measuring the plasma renin activity (PRA), plasma angiotensin II (PAII), and testosterone in the internal spermatic vein (ISV) simultaneously after treatment with hCG, and elucidated the relationship between the renin-angiotensin system and sex steroids from Leydig cells of the male gonad.