PHOSPHODIESTERASE ISOENZYMES OF THE HUMAN CAVERNOUS TISSUE AND ITS FUNCTIONAL-SIGNIFICANCE

Our study was carried out to show the existence of PDE in human penile tissue and the effect of various PDE inhibitors on its activity. Cave rnous tissue was obtained from patients underwent penectomies or penil e prosthesis implantation. The tissue was homogenized and centrifuged at 50 000 g. The supernatant fraction was applied to a DEAE-column. an d eluted using sodium acetate gradient. PDE assay was performed by mod ification of the method of Thompson and Appleman. An organ bath study was performed to evaluate the relaxing effect of various selective PDE inhibitors. We found three different PDE isoenzymes, PDE III (cGMP-in hibited), PDE IV (cAMP specific) and PDE V (cGMP-specific). Spontaneou s contractions were found in 30 % strips and could be abolished by all selective inhibitors tested. These selective PDE inhibitors relaxed n oradrenalin precontracted strips dose-dependently, PDE III inhibitor w as the most potent PDE inhibitor and possesses an EC50 equal to papave rine. The existence of three different isoenzymes has been shown in th is study. Our findings support the involvement of cyclic nucleotide me tabolism in the regulation of cavernous smooth muscle tone and open a possibility of using selective PDE inhibitor in treating erectile dysf unction.