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Cell Biology International (1997) 21, 195–200 (Printed in Great Britain)

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REGULATION OF ION TRANSPORT BY P2UPURINOCEPTORS AND α2A ADRENOCEPTORS IN HT29 CELLS

WEI ZHANG and GODFRIED M. ROOMANS

Department of Human Anatomy, University of Uppsala, Box 571, S-75123, Uppsala, Sweden

Abstract

X-ray microanalysis was applied to investigate ion transport mediated by P2Upurinoceptors and α2A adrenoceptors as well as their interaction in the regulation of the intracellular elemental concentration in HT29 cells. In response to ATP, HT29 cells showed a decrease of intracellular Cl, Na and an increase in Ca. A similar result was observed with UTP, but UTP appeared to be more potent than ATP. On the other hand, UK14,304, an α2receptor agonist, was found to be capable of reversing the action of both UTP and ATP on ion secretion, and caused a clear increase in intracellular Na and Cl. Moreover, treatment of cells with UK14,304 before exposure to UTP did not induce a decrease in Cl and Na, suggesting that UK14,304 blocks the action of UTP. The secretory effect of UTP was also blocked by NPPB, a chloride channel blocker, and alloxan. Chelation of extracellular Ca with EGTA abolished ion response to UTP. These results suggest that since inhibition of the intracellular cAMP system and chelation of Ca2+can block the nucleotide-induced chloride secretion, the ATP and UTP-induced chloride secretion can be mediated via both cAMP-dependent and Ca2+-dependent pathways.

Key words: P2Upurinoceptor, α2A adrenoceptor, UTP, ATP, UK14,304, NPPB, HT29 cells.

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