Aldosterone and the control of secretion by the nasal salt gland of the north African desert lizard, Uromastix acanthinurus

Abstract

The secretory response of the nasal salt gland of the north African agamid lizard Uromastix acanthinurus to injections of 1 M KCl and NaCl is correlated with changes in circulating levels of the corticosteroids aldosterone and corticosterone. KCl loading led to a progressive rise in plasma aldosterone levels, and NaCl loading was associated with a fall. Neither treatment significantly altered plasma corticosterone concentrations which remained at levels characteristic of unstressed animals. Rates of potassium excretion were positively correlated with circulating levels of aldosterone whereas sodium excretion showed a negative correlation. As in previous studies, injections of exogenous aldosterone or dexamethasone into KCl-loaded animals failed to further stimulate potassium excretion, but did depress sodium excretion by the gland. Spironolactone, an aldosterone antagonist in mammals, was without effect on the rate of potassium excretion in KCl-injected animals. These data suggest that aldosterone functions as a mineralocorticoid on the nasal gland of U. acanthinurus (i.e., natriferic and kaliuretic) but direct evidence of this will require the use of adrenalectomized animals.