Osmotic water flow across the abdominal skin of the toad Bufo marinus: effect of vasopressin and isoprenaline

• Published in: The Journal of physiology Vol. 329; no. 1; pp. 281 - 296
• Main Authors: de Sousa, R. C., Grosso, Alda
• Format: Journal Article
• Language: English
• Published: England The Physiological Society 01.08.1982
• Subjects: Animals; Bufo marinus; In Vitro Techniques; isoprenaline; Isoproterenol - pharmacology; Methohexital - pharmacology; osmoregulation; Osmosis - drug effects; Phentolamine - pharmacology; Propranolol - pharmacology; skin; Skin - drug effects; Skin - metabolism; Sodium - metabolism; Urinary Bladder - metabolism; vasopressin; Vasopressins - pharmacology; Water - metabolism
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.1982.sp014303

1. Net water flow J w , was measured across the abdominal skin of the toad Bufo marinus with a volumetric, automatic technique that allows for averaging J w over time intervals as short as 1 sec. 2. Basal J w was very stable and corresponded to a coefficient of osmotic flow, L PD , of ca. 15 × 10 -7 cm sec -1 atm -1 (or to an osmotic water permeability coefficient, P f , of 20 μm sec -1 ). 3. Both vasopressin and the β-adrenergic agonist, isoprenaline, triggered high hydrosmotic responses that could lead to P f values exceeding 250 μm sec -1 . The effect of isoprenaline was very reproducible while that of vasopressin varied considerably. 4. Methohexital and propranolol selectively inhibited the hydrosmotic effects of vasopressin and isoprenaline, respectively, whereas amiloride and ouabain had no effect. 5. Mutual inhibition was found between vasopressin and isoprenaline in skins very sensitive to vasopressin. In less sensitive skins isoprenaline further increased J w despite exposure of the epithelia to supramaximal concentrations of vasopressin. 6. Differential reactivity to vasopressin was found between the skin and the bladder taken from the same toad. In some instances, the bladder responded normally to vasopressin while the skin was totally unresponsive, suggesting the presence of osmoregulatory mechanisms exerting a local modulation of the vasopressin action in different target epithelia of the same animal.