title: Effects of adrenalectomy and acute replacement by corticosteroids on distal acidification.
abstract: The role of adrenocortical steroids in distal nephron acidification was studied in rats by measuring urine minus blood PCO2 differences (U-B PCO2) in control, sham-operated, and adrenalectomized (ADX) animals. Operations were performed 48 h before experiments. During the experiments, all rats received an infusion of 0.35-0.60 M NaHCO3, leading to urine bicarbonate concentrations in the order of 100-200 mM. Adrenalectomized rats had significantly decreased U-B PCO2 (11.9 +/- 1.99 mmHg; 1 mmHg = 133.3 Pa) with respect to sham-operated rats (39.9 +/- 1.26 mmHg). In another series, ADX rats received supplements of the adrenal steroids corticosterone, aldosterone, and 18-hydroxycorticosterone 100 min before the experiment. U-B PCO2 increased after hormone administration: corticosterone, 30.0 +/- 2.13 mmHg; aldosterone, 26.6 +/- 1.74 mmHg; 18-hydroxycorticosterone, 29.0 +/- 1.60 mmHg; but none restored these values to normal. Combinations of two hormones were also used; only aldosterone + corticosterone restored U-B PCO2 to normal: 39.0 +/- 1.66 mmHg. Renal phosphate excretion (but not urine phosphate levels) decreased significantly in ADX as compared with sham-operated rats. Extracellular volume was not significantly affected in ADX rats, which received ad libitum 0.9% NaCl for drinking. It is concluded that distal tubular acidification, as evaluated by U-B PCO2, is dependent on cortical steroids.
authors.affiliation: Departamento de Quimica Biologica, Facultad de Ciencias Exactas y Naturales, Buenos Aires, Argentina.
authors.forename: M C
authors.initials: MC
authors.lastname: Damasco
authors.forename: M
authors.initials: M
authors.lastname: Ansaldo
authors.forename: G
authors.initials: G
authors.lastname: Malnic
mesh_terms: D015069:18-Hydroxycorticosterone / Q000494:pharmacology; D000305:Adrenal Cortex Hormones / Q000494:pharmacology*; D000315:Adrenalectomy; D000450:Aldosterone / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000652:urine; D002245:Carbon Dioxide / Q000378:metabolism; D003345:Corticosterone / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism; D005919:Glomerular Filtration Rate / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D000305:Adrenal Cortex Hormones; D001639:Bicarbonates; D002245:Carbon Dioxide; D000450:Aldosterone; D015069:18-Hydroxycorticosterone; D003345:Corticosterone