NITRIC-OXIDE SYNTHESIS IN MYOCARDIUM FOLLOWING BURN INJURY IN RATS

We investigated nitric oxide and cyclic GMP production in myocardium e arly after burn injury in rats. Nitric oxide synthase activity was mea sured in cytosol from the left ventricular wall of burned rats. Cytoso l from control group animals was shown to contain mainly Ca2+-dependen t nitric oxide synthase (cNOS) with a small amount of Ca2+-independent nitric oxide synthase (iNOS). Following burn injury, there was a mark ed increase in iNOS activity with a peak at 8 h post-burn, however, my ocardial cNOS activity was found to decline. Parallel to iNOS inductio n there was a significant increase in myocardial nitric oxide and cycl ic GIMP production. All these changes were alleviated by treatment of the rats with dexamethasone. Since increases in cyclic GMP levels in t he heart were associated with reduced myocardial contractility, it is possible that enhanced production of nitric oxide by a Ca2+-independen t NO synthase accounts, at least in part, for the depression of myocar dial contractility seen in burn animals and patients. (C) 1998 Elsevie r Science Ltd for ISBI. All rights reserved.