Restoration by corticosteroids of the hyperaldosteronism in hyponatraemic rats with panhypopituitarism.
1. In the syndrome of inappropriate secretion of antidiuretic hormone, hyponatraemia is associated with a normal bicarbonate concentration despite dilution. This normal bicarbonate concentration is related to the development of a hyperaldosteronism, which is attributed to a direct stimulation of the zona glomerulosa by the hyponatraemic state. Some workers have suggested that, to develop this hyperaldosteronism requires the presence of a pituitary factor. To determine whether the pituitary gland plays a role in this hyponatraemia-induced hyperaldosteronism, water intoxication was performed for 24 h in normal and in panhypopituitaric rats. 2. In normal rats, hyponatraemia (108 mmol/l), induced by the administration of 1-desamino-8-D-arginine vasopressin and 2.5% D-glucose-0.45% NaCl by gavage (15% body weight) was associated with a mild increase in bicarbonate concentration, and blood acid-base equilibrium showed a mixed metabolic and respiratory alkalosis (pH 7.57, partial pressure of CO2 29 mmHg, base excess +5.5 mmol/l), and aldosterone concentration was increased 3-fold as compared with the control value. When hyponatraemia (110 mmol/l) was induced in a similar manner in panhypopituitaric rats, we observed a very low aldosterone concentration (< 50 pg/ml) and a compensated respiratory alkalosis (pH 7.45, partial pressure of CO2 30 mmHg, base excess -2.6 mmol/l). The restoration of a hyperaldosteronaemic state in this group of rats was related essentially to corticosteroid intake. 3. These data suggest that corticosteroids play a critical role in the development of hyponatraemia-related hyperaldosteronism, a phenomenon not necessarily dependent on a pituitary factor.
Unité de Recherche du métabolisme hydrominéral, Hôpital Universitaire Erasme, Université Libre de Bruxelles, Belgium.
G
G
Decaux
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L
Crenier
B
B
Namias
C
C
Gervy
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A
Soupart
D000136:Acid-Base Equilibrium / Q000502:physiology; D000472:Alkalosis, Respiratory / Q000209:etiology; D000818:Animals; D003907:Dexamethasone / Q000494:pharmacology*; D006929:Hyperaldosteronism / Q000209:etiology*; D007010:Hyponatremia / Q000097:blood / Q000150:complications* / Q000209:etiology; D007018:Hypopituitarism / Q000150:complications*; D008297:Male; D010902:Pituitary Gland / Q000503:physiopathology; D051381:Rats; D017208:Rats, Wistar; D013974:Thyroxine / Q000494:pharmacology; D014869:Water Intoxication / Q000150:complications
D003907:Dexamethasone; D013974:Thyroxine