Iodide transport in rat small intestine: dependence on calcium.
1. The involvement of calcium in the regulation of iodide secretion was investigated in stripped sheets of rat small intestine. 2. In the absence of exogenous modifiers a net iodide absorption was observed in the rat proximal intestine, whereas the mid-intestine secreted iodide. 3. Removal of Ca2+ from the bathing solutions abolished net I- secretion in the mid-intestine. The calcium channel blocker verapamil produced similar effects on net I- secretion. 4. Theophylline increased net I- secretion both in the absence and in the presence of verapamil, but the effects of theophylline were less in the presence of verapamil or in Ca2+-free media. 5. Trifluoperazine inhibited basal iodide secretion and attenuated theophylline-induced I- secretion. 6. All the modifiers which prevented net I- secretion reduced iodide fluxes across the mucosal border and increased serosal iodide exit. The opposite was observed with theophylline. 7. It is suggested that I- secretion might result from changes in both mucosal and serosal I- permeabilities, and that both processes appear to be regulated by calmodulin.
Ilundain
A
A
Departamento de Fisiologia Animal, Facultad de Farmacia, Universidad de Navarra, Spain.
Larralde
J
J
Toval
M
M
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000494:pharmacology*; D066298:In Vitro Techniques; D007421:Intestine, Small / Q000378:metabolism*; D007454:Iodides / Q000493:pharmacokinetics*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013806:Theophylline / Q000494:pharmacology; D014268:Trifluoperazine / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
D007454:Iodides; D014268:Trifluoperazine; D013806:Theophylline; D014700:Verapamil; D002118:Calcium