Toad

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

Testicular Leydig cells and 277-1277-1277-1dehydrogenase in cadmium-treated toads (Bufo melanostictus)

Abstract: Injection of cadmium chloride in toad increased Leydig cell size (area) and Δ5-3β-hydroxysteroid dehydrogenase activity in the testis.

Dopaminergic inhibition of vasopressin-stimulated water flow in the toad bladder: evidence for local formation of dopamine.

Abstract: Dopamine administration increases renal excretion of water and Na. It remains uncertain whether these effects of dopamine are the result of a hemodynamic effect or the consequence of a direct cellular action. We investigated the effect of dopamine on water transport by the isolated toad bladderin vitro. Dopamine failed to alter baseline water flow but caused a significant inhibition of arginine vasopressin (AVP) or cyclic adenosine monophosphate (AMP) stimulated water flow. The effect of dopamine on stimulated water flow was not due to activation of α adrenergic, β adrenergic, or cholinergic receptors. The selective antagonists of dopamine, metoclopramide and apomorphine, prevented the effect of dopamine on AVP-stimulated water flow. These observations suggest the existence of a dopaminergic receptor in the toad bladder.l-Dopa also inhibited AVP-stimulated water flow. The effect ofl-Dopa could be prevented by metoclopramide, thus suggesting thatl-Dopa is converted to dopamine by an aromatic amino acid decarboxylase present in the toad bladder. To investigate this possibility we measured the effect of the decarboxylase inhibitor, carbidopa, on the14CO2 production generated by decarboxylation of14Cl-Dopa in isolated toad bladder epithelial cells. Isolated toad bladder epithelial cells generated significant amounts of14CO2 from14Cl-Dopa. This effect could be blocked by carbidopa, thus suggesting the existence of an aromatic amino acid decarboxylase system in the toad bladder. Carbidopa also prevented the inhibitory effect ofl-Dopa on AVP-stimulated water flow, suggesting thatl-Dopa needs to be converted to dopamine to inhibit water flow. These data suggest the existence of a dopaminergic receptor in the toad bladder. These data also suggest that dopamine can be formed locally in the toad bladder and can thus serve as a local modulator of water transport.

3H-fucose incorporation into glycoproteins of toad bladder epithelial cells.

Abstract: Electron microscope autoradiography was used to detect the incorporation of 3H-fucose into glycoproteins of toad bladder epithelial cells. After short exposure to 3H-fucose, without a chase period, the Golgi regions of all four cell types were labeled. When exposure to 3H-fucose was followed by chase periods (1,3,4 and 6 hours) the apical and basal-lateral plasma membranes of granular cells were heavily labeled. Apical granules and the cytoplasm of granular cells were also labeled, suggesting that they both provide the means for glycoprotein transfer from the Golgi to the plasma membranes. The heaviest labeling in mitochondria-rich cells, after the 1- and 3-hour chase periods, was over the apical tubules, although the apical and basal-lateral plasma membranes were also heavily labeled. After 4- and 6-hour chases, the labeling of the apical tubules decreased, whereas the labeling of the plasma membranes increased, strongly suggesting that in these cells apical tubules play a major role in the transfer of glycoproteins from the Golgi to the plasma membrane. Our results demonstrate that the route of 3H-fucose incorporation into plasma membrane glycoproteins and the rate of glycoprotein synthesis and breakdown are not the same in the two major epithelial cell types in toad bladder.