Modulatory effect of protein kinase C activator on contractility of rat vas deferens

The modulatory effect of the protein kinase C activator was examined on contraction of rat isolated vas deferens induced by constrictive agonists, noradrenaline (NA), ATP, BaCl₂ and high K⁺. Phorbol 12,13-diacetate (PDA, 1 μmol/l) induced a transient extracellular Ca²⁺-dependent contraction while the inactive analogue, 4α-phorbol (1 μmol/l) had no effect. PDA significantly enhanced the peak amplitude of the contractile response to NA (0.1-10 μmol/l), ATP (100 μmol/l), Ba²⁺ (3 mmol/l) or high K⁺ (30 mmol/l). Staurosporine at 30 nmol/l reduced the enhancing effect of PDA on the agonist-induced contraction. NA (10 μmol/l) produced a phasic contraction followed by a sustained contraction, while ATP induced monophasic contraction. Pretreatment with nifedipine (10 nmol/l) had no effect on the phasic contraction induced by NA, but it significantly reduced ATP- or high K⁺-induced contraction. Staurosporine (30 nmol/l) alone attenuated the peak contractile response induced by NA or ATP but not by Ba²⁺. NA produced a transient contraction in Ca²⁺-free Krebs solution, and PDA (1 μmol/l) markedly enhanced this effect. These novel data indicate that activation of a protein kinase C-dependent mechanism not only affects contraction mediated by Ca²⁺ influx through voltage-sensitive Ca²⁺ channels, but also promotes intracellular Ca²⁺ release or intracellular Ca²⁺-mediated contractile mechanism in rat vas deferens. Copyright © 2001 S. Karger AG, Basel.