Short-time changes in natripheric and hydrosmotic fluxes of water and in the urine production due to and increase of the osmolarity of the external bath in the toad, Bufo arenarum

JUAN C. REBOREDA; PETRIELLA, S.; SEGURA, E. T.

Comparative Biochemistry and Physiology. A: Comparative Physiology

Año: 1987 vol. 88 p. 571 - 575

0300-9629

1. Sudden decreases in the osmotic gradient across the skin due to the replacement of water of the bath by 115 mM NaCl had no effect on water uptake of intact or hypophysectomized toads. 2. A concomitant decrease in the urine production was observed in intact but not in hypophysectomized animals. 3. Addition of amiioride chlorydrate (0.25 mM) to the 115 mM NaCl bath induced a significant decrease in water uptake both in intact and in hypophysectomized toads. 4. The osmotic permeability coefficient (Lpd) increased significantly during the osmotic gradient reduction with 115 mM NaCl plus 0.25 mM amiloride or 230 mM sucrose in both groups. 5. No changes in the plasmatic osmolarity were detected during the development of these responses to the osmotic gradient reduction. 6. These results are consistent with the hypothesis of short-term changes in the natripheric and hydrosmotic fluxes of water across the skin and in urine production triggered by the osmotic gradient reduction. The possible participation of arginine vasotocin in these responses is discussed.