Does the natriuretic hormone play a role in hypertension in South African blacks?

It has been suggested that circulating natriuretic hormone may be important in the pathogenesis of essential hypertension by inhibiting the ouabain-sensitive Na+, K+-ATPase pump and that this effect should be more pronounced in low-renin hypertensives. We have studied serum and red blood cell sodium and potassium concentrations in vitro, before and after exogenous ouabain, in White normotensives and Black subjects with essential hypertension and in two groups of renal patients. No convincing evidence of sodium or potassium inhibition could be found in Blacks with either low-renin or high-renin hypertension. Striking inhibition was seen in the renal groups, supporting a circulating natriuretic factor, but there were anomalies within the renal groups, which suggest additional cell membrane abnormalities.