Rapid activation of basolateral potassium transport in human colon by oestradiol

1 We investigated the effect of oestradiol on basolateral potassium channel s in human colonic epithelium. 2 Ion transport was quantified using short circuit current (I-sc) measureme nts of samples mounted in Ussing chambers. Serosal K transport was studied using nystatin permeabilization of the apical membrane. Intracellular pH ch anges were quantified using spectroflouresence techniques. 3 Experiments were performed with either 10 nM or 1 muM Ca2+ in the apical bathing solution. With 10 nM Ca2+ in the apical bathing solution addition o f oestradiol (1 nM) to the basolateral bath produced a rapid increase in cu rrent (DeltaI(K) = 11.2 +/- 1.2 muA.cm(-2), n = 6). This response was preve nted by treatment of the serosal membrane with tolbutamide (1 muM). With 1 muM Ca2+ in the apical bathing solution addition of oestradiol produced a r apid fall in current (DeltaI(K)=-12.8+/-1.4 muA.cm(-2)), this response was prevented by treatment of the basolateral membrane with tetra-pentyl-ammoni um (TPeA). These responses were rapid and occurred independently of protein synthesis. 4 4 Inhibition of basolateral Na+/H+ exchange with either amiloride or a low sodium bathing solution prevented this response. These responses were preve nted by inhibition of protein kinase C (PKC) with bis-indolyl-maleimide. 5 5 Oestradiol (1 nM) produced a rapid intracellular alkanization (mean incre ase=0.11 pH units; n=6; P<0.01). 6 6 These results suggest that oestradiol rapidly modulates serosal K transpo rt in human colon. These effects depend upon intact Na+/H+ exchange and pro tein kinase C. We propose a nonclassical, possibly membrane linked, mechani sm for oestradiol action in human colonic epithelium.