Effects of parathyroid hormone and calcitonin on electrolyte excretion in the rabbit.

Effects of parathyroid hormone and calcitonin on electrolyte excretion in the rabbit. We evaluated the effects of bovine parathyroid hormone (PTH) and salmon calcitonin on urinary electrolyte excretion in thyroparathyroidectomized rabbits and rats in vivo to obtain data for the isolated rabbit tubule in vitro. In rats, PTH increased fractional phosphate excretion (FE PO 4 ) in a dose-dependent fashion from 0.13 ± 0.02% to 36.0 ± 3.0%. In rabbits, FE PO 4 started at a much higher level, 18.0 ± 4.0%, and increased to 28.0 ± 4.0% with pharmacologic doses of PTH. In rats, PTH significantly decreased calcium excretion at the lowest dose, and this effect persisted at the higher doses. In rabbits, calcium excretion was markedly higher and was significantly decreased at the highest dose of PTH. In rats, calcitonin increased FE PO 4 at low dose levels without further increases at the higher dose. In contrast, calcitonin was not phosphaturic in rabbits, and at the highest dose FE PO 4 was significantly decreased. In rats, calcitonin increased FE Na from 0.2 ± 0.1% to 1.6 ± 0.5% at the highest dose. In rabbits, calcitonin was markedly natriuretic; FE Na increased from 4.0 ± 0.5% to 18.0 ± 3.0% at the low dose without further increases at the higher dose. FE Cl increased in parallel from 6.0 ± 0.6% to 23.0 ± 4.0%. Summary. PTH resulted in similar directional changes in phosphate and calcium handling in both rabbit and rat. The magnitude of response, however, varied between species. The predominant effects of calcitonin were to increase phosphate excretion in the rat and sodium chloride excretion in the rabbit. Effets de l'hormone parathyroidienne et de la calcitonine sur l'excretion d'electrolytes chez le lapin. Les effets de l'hormone parathyroidienne (PTH) bovine et de la calcitonine de saumon sur l'excretion urinaire d'electrolytes ont ete evalues in vivo chez des lapins et des rats thyroparathyroidectomises afin d'apporter des elements d'interpretation des resultats obtenus in vitro sur le tube isole de lapin. Chez les rats la PTH augmente l'excretion fractionnelle de phosphate (FE PO 4 ) de 0,13 ± 0,02% a 36,0 ± 3,0%, en fonction de la dose. Chez le lapin, FE PO 4 part d'un niveau plus eleve, 18,0 ± 4,0%, et augmente a 28,0 ± 4,0% avec des doses pharmacologiques de PTH. Chez le rat, la PTH diminue significativement l'excretion de calcium aux faibles doses, et cet effet persiste aux doses elevees. Chez le lapin, l'excretion de calcium est beaucoup plus importante et elle diminue significativement aux plus fortes doses de PTH. Chez le rat, la calcitonine augmente FE PO 4 aux faibles doses sans effet supplementaire aux fortes doses. Au contraire, chez le lapin, il n'y a pas d'effet phosphaturique, et FE PO 4 diminue significativement aux doses les plus elevees. Chez le rat, la calcitonine augmente FE Na de 0,2 ± 0,1% a 1,6 ± 0,5% aux doses les plus elevees. Chez le lapin la calcitonine est fortement natriuretique; FE Na augmente de 4,0 ± 0,5% a 18,0 ± 3,0% aux doses faibles, sans augmentation supplementaire aux doses les plus elevees. FE Cl augmente parallelement de 6,0 ± 0,6% a 23,0 ± 4,0%. Resume. La PTH determine des modifications des comportements du phosphate et du calcium qualitativement semblables chez le lapin et le rat, l'importance de la reponse varie cependans avec l'espece. Les effets preponderants de la calcitonine sont l'augmentation de l'excretion de phosphate chez le rat et de chlorure de sodium chez le lapin.