Control mechanisms of renal functions: Effects of cardiovascular drugs on vasoconstrictive and antinatriuretic stimuli in the in vivo kidney

The kidney contributes to cardiovascular homeostasis through Na+ and water excretion and renin secretion. Changes in renal functions, therefore, have a close relationship to pathophysiology of cardiovascular diseases and to d rug efficacy for them. The functions of the kidney are controlled by the sy mpathetic nervous system and various kinds of humoral factors and by their complicated interactions. Studies in the intact and working kidney in vivo have been providing physiologically significant information on the renal fu nctions and drug actions. This review, by demonstrating data obtained in ou r laboratory with experiments in anesthetized dogs in vivo, refers mainly t o the neural control of renal functions and renal actions of atrial natriur etic peptide (ANP) and an adenylate cyclase activator NKH477, either of whi ch could be used for the treatment of congestive heart failure. Electrical stimulation of the renal nerves, which could mimic the events during elevat ion of renal sympathetic nerve activity, induces frequency-dependent renal norepinephrine release, renal vasoconstriction, antinatriuresis and renin s ecretion. ANP causes potent natriuresis and suppresses the nerve stimulatio n-induced renin secretion and renal vasoconstriction without affecting the norepinephrine release. Effects of ANP on other vasoconstrictive and antina triuretic stimuli such as angiotensin II and endothelin are also demonstrat ed. Renal actions of NKH477 had been unknown, but we revealed that NKH477 e levates renal cAMP level and causes vasodilation and natriuresis. NKH477 al so suppresses the nerve stimulation-induced renal vasoconstriction, and the reby blunts the antinatriuresis. The renal actions of these drugs clarified in our study may contribute to their curative effects on congestive heart failure.