Renin and the kidney.

The factors involved in renin release have been extensively evaluated. The primary determinants are the transmural pressure at the afferent arteriole, sodium delivery to the macula densa, and the activity of the adrenergic nervous system. Other possible factors include circulating catecholamines, the serum and cerebrospinal fluid sodium concentration, serum potassium concentration, angiotensin II concentration, and antidiuretic hormone release. There is no convincing evidence that the renin-angiotensin system mediates renal autoregulation. Plasma renin activity is altered in a number of clinical settings. This parameter is elevated in most patients with cirrhosis and the nephrotic syndrome as well as in individuals with severe congestive heart failure. Despite inappropriately large weight gains, plasma renin suppresses normally with increased salt intake in edematous patients who have a normal glomerular filtration rate. The mechanisms of the alteration in the renin-angiotensin system in Bartter's syndrome is still not clear.