Ammonium chloride induced acidosis and aldosterone secretion in the goat

Responses to 30-min intraduodenal infusion of NH4Cl (total amount 75 mmol) were studied in conscious goats. The infusion caused an immediate, transient rise in plasma aldosterone concentration (PA) from a mean of 78 to 221 pmo l-1. As expected, the NH4Cl administration also induced metabolic acidosis, initially subjected to partial respiratory compensation. The acidosis did not become fully developed until 1 h after cessation of the infusion, when PA had almost returned to its initial level. Renal compensation of the acidosis was shown by acidification of the urine and reduced Na excretion being most pronounced 1-2 h post-infusion. During the infusion blood haemoglobin concentration and the haematocrit increased by 25 and 13%, respectively, without simultaneous increase in plasma protein concentration and with persisting ear vasodilatation, indicating a mobilization of stored erythrocytes in the absence of a general increase in sympathetic tone. The results suggest that the reduction of blood pH is not the cause of the increase in PA occurring in association with NH4Cl-induced metabolic acidosis, but leave open the possibility that this increase may be due to some centrally mediated or direct adrenal influence of NH+4. As regards the apparent NH4Cl-induced mobilization of stored erythrocytes, it is suggested that such a response may play a role in the defence against acidosis by increasing the buffering capacity of the circulating blood.