1. ¹Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia, USA
2. ²Department of Physiology, Medical College of Georgia, Augusta, Georgia, USA

Correspondence: CJ Wingard, Department of Physiology, Medical College of Georgia, Augusta, GA 30912, USA. E-mail: Cwingard@mail.mcg.edu

Received 11 July 2003; Revised 27 August 2003; Accepted 8 September 2003; Published online 27 November 2003.

Abstract

Constriction of the penile vasculature prevents erection and is largely mediated by physiological agonists. We hypothesized that protein kinase C (PKC) may act as a regulator of penile vascular tone. Studies were designed to identify PKC isoforms present and to investigate their roles in phenylephrine-induced muscle contraction in the isolated rat corpora cavernosa. We demonstrated the presence of PKC, , , , , , and in rat corpora cavernosa and a subcellular distribution, which favored a membrane association for PKC, , , and . Phenylephrine (3 M) generated an active stress of 9.61.5 mN/mm² and was associated with a significant increase of PKC and PKC immunoreactivity in the particulate fraction. The amount of PKC and PKC in the particulate fraction rose by 364.4 and 512.2% with phenylephrine stimulation. Furthermore, the phenylephrine concentration–response curve was potentiated in the presence of phorbol 12-myristate13-acetate (PMA) (0.1 M), a PKC activator (EC₅₀: phenylephrine 1.00.8 M vs phenylephrine+PMA 0.30.1 M) and inhibited in the presence of chelerythrine chloride (30 M), a PKC inhibitor (EC₅₀: phenylephrine 1.00.8 M vs phenylephrine+chelerythrine chloride 5.72.4 M). Based on these results, we suggest a potential role for PKC and PKC in phenylephrine-induced smooth muscle tone of the rat cavernosum.