Protective effects of antioxidative serotonin derivatives isolated from safflower against postischemic myocardial dysfunction

N-(p-Coumaroyl)serotonin (C) and N-feruroylserotonin (F) with antioxidative activity are present in safflower oil. The protective effects of C and F were investigated in perfused guinea-pig Langendorff hearts subjected to ischemia and reperfusion. Changes in cellular levels of high phosphorous energy, NO and Ca2+ in the heart together with simultaneous recordings of left ventricular developed pressure (LVDP) were monitored by an nitric oxide (NO) electrode, fluorometry and P-31-NMR. The rate of recovery of LVDP from ischemia by reperfusion was 30.8% in the control, while in the presence of C or F a gradual increase to 63.2 or 61.0% was observed. Changes of transient NO signals (T-NO) released from heart tissue in one contraction (LVDP) were observed to be upside-down with respect to transient fura-2-Ca2+ signals (T-Ca) and transient O-2 signals detected with a pO(2) electrode. At the final stage of ischemia, the intracellular concentration of Ca2+ ([Ca2+](i)) and the release of NO increased with no twitching and remained at a high steady level. The addition of C increased the NO level at the end of ischemia compared with the control, but [Ca2+](i) during ischemia decreased. On reperfusion, the increased diastolic level of T-Ca and T-NO returned rapidly to the control level with the recovery of LVDP. By in vitro EPR, C and F were found to directly quench the activity of active radicals. Therefore, it is concluded that the antioxidant effects of two derivatives isolated from safflower play an important role in ischemia-reperfusion hearts in close relation with NO.