FIGURE 3. Effect of AT1 and AT2 receptor antagonists on the AngII-induced inhibition of ROMK channels in CCDs from LK-fed rats.

A, representative channel recording obtained in a principal cell-attached patch at a holding potential of 0 mV. The inhibitory effect of AngII was completely blocked by pretreatment of the CCD with losartan (20 μM), an AT1 receptor antagonist. The top trace demonstrates the time course of the experiment; the recording is expanded below (traces 1 and 2) to show fast time resolution. The channel-closed state (“C”) is indicated by a dashed line. Current levels are indicated by the short bars on the right of each trace. B, bar graph summarizing the effects of antagonists of the AT1 receptor (losartan) and AT2 receptor (PD123319) on the AngII-induced reduction of ROMK channel activity. C, bar graph summarizing the effect of oral losartan administration (10 mg/kg/day added to the drinking water) in LK-fed rats. ROMK channel activity (NPo) in losartan-treated rats significantly exceeded that measured in LK-fed animals provided vehicle alone in drinking water.