OBJECTIVETo study regulation of Ca(2+)-activated K(+) channels (KCa) of mesenteric artery smooth muscle cell (SMC) from 21 old patients with essential hypertension (EH) by endothelin-1 (ET-1) and prostagl E(1) (PGE(1)).

METHODSMesenteric artery branch from EH was digested by enzyme. Patch clamp technique was used to pull cell-attached and inside-out patches on mesenteric artery SMC from EH and the normotensive patients respectively. The signal channel open probability (Po), open dwell-time (To) and close dwell-time (Tc), open channel number per patch were recorded. After adding Ca(2+) (10(-8) approximately 10(-6) mol/L), ET-1(2 approximately 8 x 10(9) mol/L) and PGE(1) (10, 20, 40, 100, 200, 400 nmol/L) to cytoplasm respectively. The parameters above were observed again.

RESULTSCompared to that of normotensive patients, the activities of KCa channels of patients with EH was higher. After adding Ca(2+) to cytoplasm,the Po of KCa channels in normotensive patients increased significantly. But it was few changes in EH group. KCa channels has dual reaction to ET-1 in normotensive patients. We have found no statistics difference when ET-1 present on KCa channels of EH cases. Whereas PGE(1) can affect KCa channels current and channels kinetic significantly in side-out patches. The Po of KCa channels increased. The To protracted and the Tc curtailed in EH.

CONCLUSIONSThe activities of KCa channels of patients with EH increased significantly. but the sensitive to Ca(2+) decreased. ET-1 were few effect to KCa channels. The PGE(1) can activated KCa channels of patients with EH.