K+ transport in colonocytes isolated from the chick: effect of anisosmotic buffers.
Potassium transport was measured in isolated chicken colonocytes using 85Rb+ as a tracer for K+. Rb+ was determined by atomic absorption spectrometry. The results revealed that net K+ uptake occurred via at least four mechanisms: (i) Na+,K(+)-ATPase, (ii) K(+)-ATPase, (iii) Na(+)-K(+)-2Cl- cotransport system and (iv) a mechanism(s) which is resistant to both ouabain and bumetanide. The rate of K+(Rb+) efflux is stimulated by the calcium ionophore A23187, inhibited by either quinine, verapamil or Ba2+, and unaffected by either apamin, 3,4-diaminopyridine (3,4-DAP), H2-DIDS or bumetanide. The A23187-induced increase in K+(Rb+) efflux was abolished by apamin. These findings suggest that K+(Rb+) efflux from chicken colonocytes occurs at least in part through Ca(2+)-activated K+ channels. The present results also show that all these K+ transport systems are involved in cell volume regulation. Thus, external hyposmolarity decreased net K+(Rb+) uptake mediated by Na+,K(+)-ATPase, K(+)-ATPase and the Na(+)-K(+)-2Cl- cotransporter and increased K+(Rb+) efflux rate. The opposite was observed under hyperosmotic conditions.
Calonge
M L
ML
Departamento Fisiología y Biología Animal, Facultad de Farmacia, Universidad de Sevilla, Spain.
Cano
M
M
Ilundáin
A A
AA
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D002021:Buffers; D002034:Bumetanide / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism; D027682:Cation Transport Proteins; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D002645:Chickens; D003106:Colon / Q000378:metabolism*; D009994:Osmolar Concentration; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000378:metabolism; D012414:Rubidium Radioisotopes / Q000032:analysis; D028021:Sodium-Potassium-Chloride Symporters; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D002021:Buffers; D002352:Carrier Proteins; D027682:Cation Transport Proteins; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D012414:Rubidium Radioisotopes; D028021:Sodium-Potassium-Chloride Symporters; D002034:Bumetanide; D010042:Ouabain; D000251:Adenosine Triphosphatases; C022761:potassium transporting ATPase; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium