Effects of Caffeine on Plasma Renin Activity, Catecholamines and Blood Pressure

TLDR

Whether habitual caffeine ingestion has similar effects remains to be determined. The study examined the effect of a single oral dose of caffeine on plasma renin activity, catecholamines, and cardiovascular control in nine healthy, young, non‑coffee drinkers. Using a double‑blind, randomized, cross‑over design, 250 mg caffeine or placebo was administered in a methylxanthine‑free beverage to overnight‑fasted, supine subjects who had abstained from caffeine for three weeks. Caffeine markedly increased plasma renin activity (57 %), norepinephrine (75 %), epinephrine (207 %), urinary normetanephrine (52 %) and metanephrine (100 %), raised mean blood pressure by 14/10 mm Hg, and was associated with a 20 % rise in respiratory rate, indicating potent stimulation of renin and adrenomedullary secretion.

Abstract

Using a double-blind, randomized, cross-over protocol, we studied the effect of a single dose of oral caffeine on plasma renin activity, catecholamines and cardiovascular control in nine healthy, young, non-coffee drinkers maintained in sodium balance throughout the study period. Caffeine (250 mg) or placebo was administered in a methylxanthine-free beverage to overnight-fasted supine subjects who had had no coffee, tea or cola in the previous three weeks. Caffeine increased plasma renin activity by 57 per cent, plasma norepinephrine by 75 per cent and plasma epinephrine by 207 per cent. Urinary normetanephrine and metanephrine were increased 52 per cent and 100 per cent respectively. Mean blood pressure rose 14/10 mm Hg one hour after caffeine ingestion. There was a slight fall and then a rise in heart rate. Plasma caffeine levels were usually maximal one hour after ingestion but there was considerable individual variation. A 20 per cent increase in respiratory rate correlated well with plasma caffeine levels. Under the conditions of study caffeine was a potent stimulator of plasma renin activity and adrenomedullary secretion. Whether habitual ingestion has similar effects remains to be determined.