EFFECT OF ISOSORBIDE-5-MONONITRATE ON PLASMA AND URINE LEVELS OF CYCLIC-GMP IN RELATION TO EXERCISE IN CORONARY PATIENTS COMPARED WITH CONTROL SUBJECTS

Nitric oxide (NO) and atrial natriuretic peptide (ANP) relax vascular smooth muscle increasing levels of cyclic guanosine 3':5' monophosphat e (cGMP). Nitrovasodilators act as exogenous nitric oxide donors. The aim of this study was to ascertain the response of cGMP to exercise wi thout medication and after the administration of 20 mg of isosorbide-5 -mononitrate (IS-5-MN) in coronary patients (n = 8) and healthy contro l subjects (n = 9). A third group of 10 normal volunteers was studied to test plasma cGMP response to second exercise test without IS-5-MN a dministration. Plasma cGMP increased significantly in both patients (P < 0.02) and controls (P < 0.01) after the first ergometry. After IS-5 -MN administration, plasma cGMP did not increase either before or afte r exercise. In normal volunteers without IS-5-MN plasma cGMP increased significantly after first (P < 0.004) and second (P < 0.0008) exercis e test. In conclusion, plasma cGMP increases during exercise. Administ ration of IS-5-MN does not raise plasma cGMP and neither does performa nce of further exercise after its administration.