The kinetics and concentration‐effect relationships of circulating adrenaline in man [proceedings]

Zurcher, 1976) during an infusion of (-)-adrenaline (0.10 ,ug kg-' min-1) in six normotensive volunteers.The mean supine plasma adrenaline was 0.29 + 0.06 nm and clearance was 114.33 + 19.73 gl kg-' min-1 (range 64.66 -189.39 ml kg-1 min-1).The mean estimate of the rate of adrenaline release was 2.82 + 0.76 nM/min (range 1.4-6.0nM/min).A comparable study of noradrenaline kinetics (FitzGerald, Hossmann, Hamilton, Reid, Davies & Dollery, 1979) suggests that the higher circulating plasma levels of noradrenaline (1.12 + 0.12 nM) may reflect both a higher rate of release (5.01 + 1.89 nM/min) and a lower rate of clearance (38.0 + 13.8 gd kg minm )of noradrenaline than adrenaline.The same subjects were infused with (-)-adrenaline at 0.01, 0.03, 0.05, 0.075 and 0.10 gg kg-' min-'.Plasma adrenaline was raised from a mean pre- infusion 0.25 + 0.03 nM to 4.61 + 0.57 nM during the final increment.The mean supine plasma adrenaline reported by Franco Morselli et al. (1977) (0.5 + 0.05 nM) was less than that attained by the infusion of exogenous (--adrenaline at 0.01 gig kg-' min-' which had a minimal haemodynamic effect (A blood pressure: +(1.95 + 0.3)/-(4.6 + 1.3) mm Hg; A heart rate +(5.1 + 1.0) beats/min).Although a linear rela- tionship with increasing log plasma adrenaline was demonstrated for responses mediated by the postsynaptic fl-adrenoceptor (blood glucose, r = 0.93; free fatty acids r = 0.97; plasma renin activity r = 0.93; plasma cyclic AMP r = 0.95) plasma noradrenaline did not change.Considerable differences in clearance limit the use of plasma adrenaline as an index of sympathomedullary activity between individuals.Increased levels of circulating adrenaline are unlikely to be of primary importance in essential hypertension. References