Six days after local exposure of the rat liver (during operation) to ultrasound (2 W/cm2, 1 min), the cytochrome P-450 content in the microsomal fraction reduced, and the rate of NADPH oxidation, the NADPH cytochrome P-450 reductase activity, ethylmorphine demethylation and aniline hydroxylation decreased in 12 days the activity of NADPH-cytochrome b5 reductase and cytosol sulfobromophthalein-glutathione-S-transferase also reduced. Heparin administration (250 U/kg i.m. every other day 3 and 6 times) had an enzyme-activating effect (particularly in the late-term restoration period) in animals which had been exposed to ultrasound.