The effects of 5-fluorouracil on contractility and oxygen uptake of the isolated perfused rat heart.

Clinical cardiotoxicity related to 5-fluorouracil (5-FU) simulates either myocardial ischemia or left ventricular dysfunction. In order to characterize the changes occurring in the heart following 5-FU administration, the isovolumic perfused rat heart model according to Langendorff has been used. Particular emphasis was laid on contractility and oxygen uptake. Perfusion of isolated hearts with 1 mg/L 5-FU for 80 minutes failed to show any differences in contractility and oxygen consumption in comparison with the control group. On the contrary, 5-FU pretreatment of Wistar rats (50 mg/kg I.P. for 5 consecutive days) led to a decrease in inotropism without any change in maximum relaxation rate. The most significant finding was the consistent increase in oxygen consumption throughout the 80 minutes of perfusion (p less than 0.05) associated with a decrease in the fractional extraction of oxygen. Mean coronary flow was consistently increased in the 5-FU-pretreated group. Lactate release and CK Leakage did not differ in the two groups. In the 5-FU-pretreated group the ratio of oxygen consumption to rate-pressure product remained significantly elevated throughout 80 minutes of perfusion in comparison with the control group (p less than 0.05). Inappropriately high oxygen uptake could be a reflection of cellular metabolic disturbances responsible for post-ischemic dysfunction.