Effects of dopamine on ion transport across the rat distal colon.
Dopamine (5.10(-6)-5.10(-4) M) induced a concentration-dependent decrease in short-circuit current (I(sc)) across the rat distal colon. This response was preceded by a transient and inconsistent increase in I(sc). The alpha-adrenoceptor blocker phentolamine and the inhibitors of dopamine-2-like (D(2)-like) receptors L-741,626 and L-745,870 inhibited the dopamine response, suggesting a contribution of adrenergic and dopaminergic receptors. The decrease in I(sc) evoked by dopamine was inhibited by bumetanide, an inhibitor of the basolateral Na(+)-K(+)-2 Cl(-) cotransporter responsible for the uptake of K(+), and by quinine, a blocker of apical K(+) channels, indicating that stimulation of K(+) secretion contributes to the measured change in I(sc). In patch-clamp experiments dopamine hyperpolarized the membrane and increased cellular K(+) current. This response was not concomitant with a change in the intracellular [Ca(2+)] as demonstrated in parallel fura-2 experiments. These results demonstrate that dopamine, like other catecholamines, stimulates colonic K(+) secretion.
Al-Jahmany
Abed A
AA
Institut für Veterinär-Physiologie, Justus-Liebig-Universität Giessen, Frankfurter Strasse 100, 35392 Giessen, Germany.
Schultheiss
Gerhard
G
Diener
Martin
M
D018674:Adrenergic Antagonists / Q000494:pharmacology; D000818:Animals; D002034:Bumetanide / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D003106:Colon / Q000187:drug effects* / Q000378:metabolism; D004298:Dopamine / Q000494:pharmacology*; D018491:Dopamine Agonists / Q000494:pharmacology; D005456:Fluorescent Dyes; D016257:Fura-2; D066298:In Vitro Techniques; D017136:Ion Transport / Q000187:drug effects*; D008564:Membrane Potentials / Q000187:drug effects; D018408:Patch-Clamp Techniques; D010646:Phentolamine / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D018674:Adrenergic Antagonists; D002712:Chlorides; D018491:Dopamine Agonists; D005456:Fluorescent Dyes; D002034:Bumetanide; D011188:Potassium; D002118:Calcium; D016257:Fura-2; D004298:Dopamine; D010646:Phentolamine