Soluble guanylate cyclase and cGMP-dependent protein kinase I expression in the human corpus cavernosum

Nitric oxide (NO) as a mediator in smooth muscle cells causes rapid and rob ust increases in cGMP levels. The cGMP-dependent protein kinase I has emerg ed as an important signal transduction mediator for smooth muscle relaxatio n. The purpose of this study was to examine the existence and distribution of two key enzymes of the NO/cGMP pathway, the cGMP-dependent kinase I (cGK I) and the soluble guanylate cyclase (sGC) in human cavernosal tissue. The expression of the enzymes were examined in corpus cavernosum specimens of 23 patients. Eleven potent patients suffered from penile deviations and were treated via Nesbit's surgical method. Nine long-term impotent patients underwent implantation of flexible hydraulic prothesis. Three potent patie nts underwent trans-sexual operations. Expression of the sGC and cGK I were examined immunohistochemically using specific antibodies. In all specimens of cavernosal tissue a distinct immunoreactivity was obser ved in different parts and structures, We found a high expression of sGC an d cGK I in smooth muscle cells of vessels and in the fibromuscular stroma. The endothelium of the cavernosal sinus, of the cavernosal arteries, and th e cavernosal nerve fibers showed an immunoreactivity against sGC. The distr ibution analysis of cGK I revealed a predominately vesicular localization i n smooth muscle cells. The examination of the endothelium showed no clear i mmunoreactivity against cGK I. There was no distinct difference in immunore activity and cellular distribution between potent and impotent patients, cGMP-dependent kinase I is predominately expressed in cavernosal smooth mus cle cells. sGC is expressed in smooth muscle cells, endothelium and nerve f ibers of the corpus cavernosum In this study, there is no correlation betwe en the distribution of soluble guanylate cyclase and cGMP dependent kinase I in potent or impotent patients.