Atrial natriuretic factor receptor heterogeneity and stimulation of particulate guanylate cyclase and cyclic GMP...

Since the seminal discovery by deBold that atria contain factors that produce diuresis and natriuresis, the biologic effects attributed to ANF have expanded to the point where the name "atrial natriuretic factor" seems inappropriate. In addition to promoting diuresis and natriuresis, ANF has been shown to produce vascular smooth muscle relaxation and to inhibit the secretion of aldosterone from the adrenal cortex, renin from the juxtaglomerlular apparatus, vasopressin from the hypothalamus, and salt and water intake after central administration. ANF also promotes intestinal secretion and stimulates testosterone synthesis in Leydig cells. However, the cellular mechanisms whereby ANF elicits these diverse effects are poorly understood. ANF has been reported to inhibit adenylate cyclase in a number of tissues. However, the significance of ANF inhibition of adenylate cyclase is unknown. This effect cannot be associated with vascular relaxation since decreased cyclic AMP would be expected to promote contraction rather than relaxation. ANF inhibition of adenylate cyclase may mediate the inhibitory effects of ANF on hormone secretion from the anterior pituitary gland. The inhibition of adenylate cyclase could also explain the inhibitory effect of ANF on aldosterone synthesis, since agents that stimulate cyclic AMP increase aldosterone synthesis. However, ANF also inhibits the dibutyryl-cyclic AMP-induced stimulation of aldosterone secretion, suggesting that an inhibition of adenylate cyclase cannot account fully for the inhibitory effects of ANF on aldosterone synthesis. There is no evidence to support a role for cyclic AMP in the diuretic and natriuretic action of ANF. An inhibition of membrane phosphoinositide breakdown by ANF and the subsequent formation of IP3 and intracellular calcium release could explain the inhibitory effects of ANF on vascular contraction and steroid synthesis. However, there is very little evidence to suggest that ANF regulates phosphoinositide metabolism, while some recent studies suggest that ANF may regulate calcium fluxes in vascular tissue. Clearly, cyclic GMP has emerged as the most likely intracellular mediator of ANF effects. ANF increases cyclic GMP in a wide range of tissues by selectively activating particulate guanylate cyclase. However, it is not known which effects of ANF are mediated by cyclic GMP. The discovery that ANF increases cyclic GMP in vascular tissue clearly suggests that cyclic GMP mediates the vascular relaxation effect of ANF, since other classes of vasodilators also increase cyclic GMP. There is preliminary evidence that cyclic GMP may inhibit renin secretion and sodium transport in kidney cells.(ABSTRACT TRUNCATED AT 400 WORDS)