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K+ transport in colonocytes isolated from the chick: effect of anisosmotic buffers
Author(s) -
Calonge ML,
Cano M,
Ilundain AA
Publication year - 1998
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/expphysiol.1998.sp004144
Subject(s) - cotransporter , chemistry , bumetanide , dids , efflux , ouabain , apamin , ion transporter , symporter , ionophore , osmotic concentration , verapamil , potassium , calcium , atpase , biophysics , sodium , biochemistry , transporter , biology , membrane , enzyme , organic chemistry , gene
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.