THE USE OF RADIOACTIVE MICROSPHERES TO COMPARE THE EFFECTS OF HYDRALAZINE, GUANETHIDINE AND SK&F 24260 ON THE REDISTRIBUTION OF CARDIAC OUTPUT IN ANAESTHETIZED RABBITS

Abstract

The use of radioactive microspheres is described for the measurement of cardiac output in anaesthetized rabbits and its redistribution after the administration of drugs which lower blood pressure. Hydralazine increased peripheral vascular conductance by 123%. The vascular beds in which it had most effect were those of the carcass (mainly muscle) and the kidneys. SK&F 24260, (1,4 dihydro‐2, 6‐dimethyl‐4‐(2‐trifluormethylphenyl)‐3,5,‐pyridinedicarboxylic acid diethyl ester), had similar vasodilator actions. Its effect in the carcass contributed relatively more to the increase of total peripheral conductance. It also caused a remarkable degree of cerebral vasodilatation. Guanethidine had a relatively small effect on total peripheral conductance and lowered blood pressure mainly by reducing stroke volume and cardiac output. 1975 British Pharmacological Society