The effect of the K(
ATP) channel opener
ZD6169 [(S)-N-(4-benzoyl-phenyl)-3,3, 3-trifluoro-2-hydroxy-2-methyl-
propionamide] currently under development for the treatment of
urinary incontinence was explored in acutely isolated adult feline ventricular myocytes.
ZD6169 activated a current over a wide range of concentrations (0.1-100 microM) that is completely blocked by 10 microM
glyburide thereby identifying it as I(K(
ATP)). The maximum activation of K(
ATP) current was observed
at 10 microM; higher concentrations decreased current activation. In contrast, the standard K(
ATP) channel opener
cromakalim showed a more usual concentration-response relationship, with increasing current for increased concentrations and no signs of saturation or reversal. The bell-shaped dose-response relationship for
ZD6169 activation of I(K(
ATP)) has also been seen in bladder myocytes, albeit at a lower concentration, and it has been proposed to contribute to the reported lack of in vivo cardiovascular side effects. We compared the effects of
ZD6169 to
cromakalim and showed that both compounds dramatically shorten cardiac myocyte action potential duration and that
ZD6169 does so in spite of the bell-shaped concentration-response relationship for activation of K(
ATP) current.