EFFECT OF CONTRAST-MEDIUM ON CORPUS CAVERNOSUM SMOOTH-MUSCLE

RATIONALE AND OBJECTIVES. Changes in contractility of corpus cavernosu m (CC) smooth muscle caused by radio contrast medium may result in mis interpretations of cavernosography used diagnostically in erectile dys function. METHODS. The authors investigated the direct effect of vario us contrast media on rabbit CC smooth muscle tissue strips in a in vit ro model by adding contrast medium to the tissue in a perfusion bath a nd recording the resulting contractions. Glucose addition was used as control. RESULTS. Application of high-osmolar, ionic contrast medium d iatrizoate-induced CC smooth muscle contractions of 57% of the control potassium chloride (124 mM) induced contractions. The low-osmolar (86 2 mOsm/kg) nonionic monomer contrast medium, iohexol, and the iso-osmo lar (300 mOsm/kg) nonionic dimer contrast medium, iodixanol, elicited contractions of 34% and 36% of the potassium chloride control contract ions, respectively. High- and iso-osmolar glucose solutions caused con tractions of 51%, 38%, and 24% of the control, respectively. Cyclic ad enosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) regulate CC smooth muscle contractions. These are influenced by diffe rent drugs including phosphodiesterases (PDEs), forskolin, and 3-morph olinsydnonimine hydrochloride (SIN-1). The nonspecific PDE inhibitors papaverine (0.1 mM) and theophylline (1 mM) reduced the contrast mediu m-induced contractions to 66% and 69%, respectively. The specific PDE inhibitor milrinone (0.1 mM) reduced the contractions to 69%; 0.1 mM f orskolin and SIN-1 reduced the contractions to 34% and 41%, respective ly. CONCLUSIONS. Contrast medium induces CC smooth muscle contractions , depending mainly on the osmolality of the solution. The contractions are reduced but not abolished by elevating the intracellular cAMP and cGMP concentrations. The clinical applications in cavernosography are discussed.