title: Effects of parathyroid hormone on urinary acidification in the rat.
abstract: To evaluate the effects of parathyroid hormone (PTH) on urinary acidification parameters, thyroparathyroidectomy was performed in normal (TPTX) and in calcium-supplemented rats (TPTX + Ca2+). Both groups were supplemented with thyroxin. Glomerular filtration rate (GFR) fell from 7.79 +/- 0.33 in the control group (C) to 4.88 +/- 0.26 ml min-1 kg-1 in TPTX, while net acid excretion fell from 5.65 +/- 0.22 in C to 3.76 +/- 0.25 mumol min-1 kg-1 in TPTX. Kinetic data of urinary acidification obtained by microperfusion techniques in proximal tubules showed that the half-time of acidification (t/2) rose from 4.75 +/- 0.24 s in C to 8.97 +/- 0.64 s in TPTX and persisted elevated in TPTX + Ca2+ (7.40 +/- 0.43 s); in the latter group, stationary pH was not significantly different from that of the control group. Bicarbonate reabsorption (JHCO3) fell from 2.18 +/- 0.15 in C to 0.823 +/- 0.082 in TPTX and was 1.53 +/- 0.073 nmol s-1 cm-2 in TPTX + CA2+. These data suggest that normal pH gradients depend on normal calcium levels, but acidification half-times are dependent on PTH, which also contributes to keeping glomerular hemodynamics and acidification rates at normal levels.
authors.affiliation: Departamento de Fisiologia, Escola Paulista de Medicina, São Paulo, Brasil.
authors.forename: F
authors.initials: F
authors.lastname: Zaladek-Gil
authors.forename: V L
authors.initials: VL
authors.lastname: Costa-Silva
authors.forename: G
authors.initials: G
authors.lastname: Malnic
mesh_terms: D000138:Acidosis / Q000652:urine*; D000818:Animals; D001639:Bicarbonates / Q000652:urine*; D007668:Kidney / Q000503:physiopathology*; D008297:Male; D010281:Parathyroid Hormone / Q000494:pharmacology*; D016105:Parathyroidectomy; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D001639:Bicarbonates; D010281:Parathyroid Hormone