Effect of catecholamines and angiotensin on extracellular water and cation movements and the effect of alpha and beta-adrenoceptor blockade.

1. The extracellular fluid volume (ECFV), as raffinose space, and its content of Na, K and Ca were measured in anaesthetized dogs in acute experiments before and during the vascular response to intravenous injections and infusions of noradrenaline, adrenaline, isoprenaline and angiotensin.2. In male dogs the effect of noradrenaline was unpredictable, the ECFV might increase or decrease. In female dogs noradrenaline caused an increase in the ECFV. The difference between the responses of the two sexes was statistically significant (P<0.001). After phentolamine, noradrenaline exerted no effect at all in either sex. After bretylium the results were like those in normal animals.3. In both males and females adrenaline generally induced an increase in the ECFV. After phentolamine, adrenaline decreased the ECFV in males and caused little change in females. The differences before and after blockade were statistically significant (P<0.001). After bretylium the results in both sexes were like those in normal animals.4. In both male and female dogs isoprenaline induced an increase in the ECFV and the results were the same as in the normal animals after both phentolamine and bretylium.5. In male dogs there was no change in the ECFV as a result of administering angiotensin, either alone or in the presence of phentolamine or bretylium. In normal females angiotensin induced a decrease in ECFV and the difference between the responses of the males and females was statistically significant (P<0.005). In females which had received either phentolamine or bretylium the results were indistinguishable from those in the males.6. Blockade of the beta-adrenoceptors with pronethalol in a few animals did not change the response to the drugs from those seen in normal animals.7. The cation content of the ECF changed in the same direction and to about the same extent as the water, except after noradrenaline when in some experiments the proportionate change in potassium concentration was considerably greater than that of the other substances.8. The inulin space and its Na and K content were measured in several dioestrous, oestrous and pro-oestrous rats and in normal and stilboestrol treated males before and after giving an intravenous injection of angiotensin. There was little difference between the results of control injections of 0.9% saline solution and of angiotensin in dioestrous and oestrous females and normal males. On the other hand, pro-oestrous females and stilboestrol treated males responded alike to angiotensin in the form of a decrease in ECFV which was statistically different from the responses in the other three groups (P<0.0005).9. It is suggested that the various results depend on two factors: the site of action of the drug-for example, whether it increases or decreases capillary pressure and therefore, fluid transfer-and also the sex of the animal. The ground substance of the small blood vessels is probably important in taking up and releasing fluid, and its capacity for so doing may well vary with the amount of available oestrogen. It appears that the effect of oestrogens and events at the alpha-adrenoceptor site are connected in some way.