title: Site-specific regulation of ion transport by prolactin in rat colon epithelium.
abstract: The effect of prolactin (PRL) on ion transport across the rat colon epithelium was investigated using Ussing chamber technique. PRL (1 μg/ml) induced a sustained decrease in short-circuit current (I(sc)) in the distal colon with an EC(50) value of 100 ng/ml and increased I(sc) in the proximal colon with an EC(50) value of 49 ng/ml. In the distal colon, the PRL-induced decrease in I(sc) was not affected by Na(+) channel blocker amiloride or Cl(-) channel blockers, NPPB, DPC, or DIDS, added mucosally. However, the response was inhibited by mucosal application of K(+) channel blockers glibenclamide, quinidine, and chromanol 293B, whereas other K(+) channel blockers, Ba(2+), tetraethylammonium, clotrimazole, and apamin, failed to have effects. The PRL-induced decrease in I(sc) was also inhibited by Na(+)-K(+)-2Cl(-) transporter inhibitor bumetanide, Ba(2+), and chromanol 293B applied serosally. In the transverse and proximal colon, the PRL-induced increase in I(sc) was suppressed by DPC, glibenclamide, and bumetanide, but not by NPPB, DIDS, or amiloride. The PRL-induced changes in I(sc) in both distal and proximal colon were abolished by JAK2 inhibitor AG490, but not BAPTA-AM, the Ca(2+) chelating agent, or phosphatidylinositol 3-kinase inhibitor wortmannin. These results suggest a segment-specific effect of PRL in rat colon, by activation of K(+) secretion in the distal colon and activation of Cl(-) secretion in the transverse and proximal colon. Both PRL actions are mediated by JAK-STAT-dependent pathway, but not phosphatidylinositol 3-kinase pathway or Ca(2+) mobilization. These findings suggest a role of PRL in the regulation of electrolyte transport in mammalian colon.
authors.affiliation: Department of Physiology, Faculty of Medicine, Srinakharinwirot University, Sukhumvit 23, Wattana, Bangkok 10110, Thailand. chatsri@swu.ac.th
authors.forename: Chatsri
authors.initials: C
authors.lastname: Deachapunya
authors.forename: Sutthasinee
authors.initials: S
authors.lastname: Poonyachoti
authors.forename: Nateetip
authors.initials: N
authors.lastname: Krishnamra
mesh_terms: D000818:Animals; D018118:Chloride Channels / Q000037:antagonists & inhibitors; D002712:Chlorides / Q000378:metabolism; D003106:Colon / Q000187:drug effects* / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D017136:Ion Transport / Q000187:drug effects* / Q000502:physiology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D008297:Male; D011188:Potassium / Q000378:metabolism; D026902:Potassium Channel Blockers / Q000494:pharmacology; D011388:Prolactin / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D026941:Sodium Channel Blockers / Q000494:pharmacology; D020032:Tyrphostins / Q000494:pharmacology
chemical_list: D018118:Chloride Channels; D002712:Chlorides; D004791:Enzyme Inhibitors; D026902:Potassium Channel Blockers; D026941:Sodium Channel Blockers; D020032:Tyrphostins; C095512:alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide; D011388:Prolactin; D011188:Potassium