The KCa channel is an important modulator of corporal smooth muscle tone and erectile capacity. In this regard, intracavemous injection of the hSlo KCa cDNA in a rat model produced a significant increase in nerve-stimulated intracavernous pressure responses, compared to control animals. The goal of the present studies was to further assess the characteristics of the KCa channel in human corporal smooth muscle. Northern blots revealed similar levels of the hSlo KCa cDNA on frozen tissue and cultured cells derived from human corpora. Steady-state and kinetic studies were conducted on corporal tissue strips precontracted with phenylephrine (PE) or endothelin-1 (ET-1) (to ∼75% of maximum) in the absence and presence of the following KCa channel blockers; 1 mM tetraethylammonium or 1 μM carybdotoxin. Both K channel blockers produced roughly 20-30% increases in the magnitude of the PE- & ET-1-induced contractile response, while also halving the time required to acheive 1/2 maximal PE, but not ET-1 response (p<0.05). Elisa assays on CAT transfected smooth muscle cells documented that 4 hours of lipofectamine transfection resulted in optimal CAT gene expression. Ca2+ imaging experiments conducted on fura-2 loaded smooth muscle cells transfected under identical experimental conditions with hSlo cDNA revealed that both resting and ET-1-induced intracellular calcium levels were significantly lower in the transiently transfected cell population (p<0.05). This provides further evidence for the potential utility of intracavernous gene therapy in the treatment of erectile dysfunction.
|State||Published - Dec 1 1997|