Toad

About: Toad is a research topic. Over the lifetime, 1624 publications have been published within this topic receiving 28732 citations.

Localization of Physiological Receptor Sites for Aldosterone in the Bladder of the Toad, Bufo tnarinus

Abstract: Nuclei were isolated from the mucosal epithelial cells of the toad (Bufo marinus) bladder by 3 methods using: (a) citric acid and Tween-80, (b) 0.17m sucrose and Triton X-100, and (c) 2.2m sucrose. Binding studies, using a competitive displacement technique, were carried out using these nuclear isolation methods. Nuclei separated by the detergent methods gave no evidence of bound aldosterone, but nuclei isolated in 2.2m sucrose were shown to contain bound hormone. Binding studies using other mineralocorticoids, an aldosterone antagonist, and inactive steroids as displacers, were carried out to demonstrate the physiological activity of the nuclear receptor sites. 9α-Fluorocortisol, deoxycorticosterone, cortisol and spirolactone SC 14266 all displaced 3H-d-aldosterone from its receptor sites. Testosterone and cholesterol gave no indication of displacement ability. The isolated nuclei were found to contain a large fraction of the aldosterone bound in the whole tissue. (Endocrinology 82: 1163, 1968)

Angiotensin II Stimulates Cutaneous Drinking in the Toad Bufo punctatus

Abstract: The renin-angiotensin system regulates drinking in many vertebrates but has not been thought to serve this function in amphibians because injections of angiotensin II (AII) have failed to stimulate either oral or cutaneous drinking. We tested the effects of intraperitoneal injections of AII on the duration of water absorption behavior and water weight gain of the red-spotted toad, Bufo punctatus. We found that doses of 1, 5, and 200 μg AII/100 g body weight significantly increased both the duration of water absorption behavior and water weight gain. The effect was eliminated by prior injection of saralasin (a specific competitive inhibitor of AII). This suggests that the mechanism that regulates hydration in amphibians is homologous to thirst mechanisms in other vertebrates and may represent an important step in the evolution of thirst in terrestrial vertebrates.

Evidence for involvement of microtubules in the action of vasopressin in toad urinary bladder. I. Functional studies on the effects of antimitotic agents on the response to vasopressin.

Abstract: The antimitotic agents colchicine, podophyllotoxin, and vinblastine inhibit the action of vasopressin and cyclic AMP on osmotic water movement in the toad urinary bladder. The alkaloids have no effect on either basal or vasopressin-stimulated sodium transport or urea flux across the tissue. Inhibition of vasopressin-induced water movement is half-maximal at the following alkaloid concentrations: colchicine, 1.8 X 10(-6) M; podophyllotoxin, 5 X 10(-7)M; and vinblastine, 1 X 10(-7)M. The characteristics of the specificity, time-dependence and temperature-dependence of the inhibitory effect of colchicine are similar to the characteristics of the interaction of this drug with tubulin in vitro, and they differ from those of its effect on nucleoside transport. Inhibition of the vasopressin response by colchicine, podophyllotoxin, and vinblastine is not readily reversed. The findings support the view that the inhibition of vasopressin-induced water movement by the antimitotic agents is due to the interaction of these agents with tubulin and consequent interference with microtubule integrity and function. Taken together with the results of biochemical and morphological studies, the findings provide evidence that cytoplasmic microtubules play a critical role in the action of vasopressin on transcellular water movement in the toad bladder.