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  • Title: K+ transport in colonocytes isolated from the chick: effect of anisosmotic buffers.
    Author: Calonge ML, Cano M, Ilundáin AA.
    Journal: Exp Physiol; 1998 Sep; 83(5):629-38. PubMed ID: 9793783.
    Abstract:
    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.
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