Plasma renin activity in acute respiratory acidosis

Plasma renin activity in acute respiratory acidosis and the effect of hexamethonium bromide was studied. Fourteen mongrel dogs were anesthetized with sodium pentobarbiturate and given 5% and 15% carbon dioxide in room air, successively. Hexamethonium bromide was given to 8 dogs prior to carbon dioxide inhalation. Arterial carbon dioxide partial pressure, oxygen partial pressure and pH were measured in addition to the determination of plasma renin activity. Plasma renin activity was elevated in moderate respiratory acidosis induced by 5% carbon dioxide inhalation from 37.5 +/- 8.8 ng/ml to 52.8 +/- 7.0 ng/ml. In severe respiratory acidosis produced by 15% carbon dioxide inhalation, plasma renin activity elevated further to 85.8 +/- 8.6 ng/ml. Plasma renin activity of the hexamethonium bromide treated dogs was 19.0 +/- 3.5 ng/ml during room air breathing. The activity was elevated to 26.0 +/- 6.4 ng/ml by 5% carbon dioxide inhalation and further to 57.3 +/- 5.9 ng/ml by 15% carbon dioxide inhalation. These findings may suggest that the elevation of plasma renin activity in acute respiratory acidosis induced by carbon dioxide inhalation is independent from sympathetic stimulation.