Key result
U-89232 induces selective vascular relaxation with minimal effect on cardiac muscle tension.
Why the study?
The distinct effects and mechanisms of potassium channel openers cromakalim, pinacidil, and the cromakalim analog U-89232 on vascular and cardiac tissues were not fully characterized.
U-89232 possesses a unique pharmacological profile compared to other potassium channel openers, causing vascular relaxation without significantly decreasing cardiac muscle tension.
Answers are grounded in this paper and cite their sources.
U-89232 shows vascular selectivity in isolated tissues; leaves open its potential as a cardiac-sparing vasodilator pending in vivo studies.
ATP-sensitive potassium (K+ATP) channel openers such as cromakalim and pinacidil exhibit both potent vasodilatory and anti-ischemic properties. U-89232, a cyanoguanidine analog of cromakalim, has recently been found to exhibit myocardial protection during ischemia without altering in vivo hemodynamics. We examined the effects of U-89232, cromakalim and pinacidil in isolated vascular and cardiac tissue and tested whether glyburide, a KATP channel blocker, could antagonize their effects. All three compounds produced concentration-dependent relaxation in isolated vascular segments, with cromakalim being approximately 100-fold more potent than either pinacidil or U-89232. Glyburide completely antagonized the effects of pinacidil but merely blunted the effects of cromakalim and U-89232. In an isolated rabbit cardiac tissue preparation, U-89232 had little effect on maximum tension in cardiac muscle, whereas cromakalim and pinacidil significantly decreased maximum developed tension in a concentration-dependent manner. Glyburide effectively antagonized the effects of cromakalim and pinacidil in cardiac tissue. These data suggest that U-89232, although chemically related to cromakalim, possesses activity which is not common to known potassium channel openers.
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Norman et al. (2008) studied Isolated vascular and cardiac tissue. U-89232, cromakalim, and pinacidil was evaluated on Vascular relaxation and cardiac muscle maximum tension. U-89232 produced concentration-dependent relaxation in isolated vascular segments but had little effect on maximum tension in cardiac muscle, distinguishing it from other potassium channel openers.
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