Effect of birch bark dry extract on the key biotransformation enzymes (cytochrome P-450) and microsomal membranes in rat liver

Birch (Betula) bark dry extract (BDE) preparations (B, V, and, especially, S types) produce a significant dose-dependent increase in the monooxygenase activity and especially in the hydroxylase activity of cytochrome P-450 in vitro in liver microsomes of intact rats. BDE of type S also produces this effect upon systemic administration in a dose of 5 mg/kg in rats with model CCl4 hepatitis. BDE dry extract possesses membranotropic and membranoprotective properties, in particular, increases the rate constant of binding of a fluorescent probe (3-methoxybenzanthrone, MBA) with intact microsomal membranes in vitro and normalizes the probe association (rate constant and strength of MBA binding) with microsomal membranes of CCl4-intoxicated rat liver in vivo (upon a systemic administration in a dose 5 mg/kg). BDE increases the activity of cytochrome P-450, especially its hydroxylating effect, both in vitro and in vivo. It is suggested that the membranotropic properties of BDE can be used for the regulation of molecular mechanisms involved in the activity of cytochrome P-450, which is a key enzyme of biotransformation.