Comparative effects of adenosine and adenine and guanine nucleotides on drug biotransformation in rats.

The effect of various nucleotides and adenosine on the hepatic biotransformation of hexobarbital sodium (HB) and p-chloro-N-methylaniline (PCMA) was determined in male rats. Intraperitoneal administration of dibutyryl cyclic adenosine 3',5'-monophosphate (DBcAMP), alone and in combination with theophylline, and the cyclic adenosine 3',5'-monophosphate (cAMP)-theophylline combination prolonged HB sleeping time by more than 70%. cAMP or dibutyryl cyclic guanosine 3',5'-monophosphate (DBcGMP), alone or in combination with theophylline, failed to significantly alter the duration of HB-induced hypnosis. Plasma levels of HB upon awakening suggested that the increase in sleeping time was apparently not due to an altered sensitivity of the brain to the barbiturate. The effect appears to be related to an impairment of HB metabolism since only those compounds that inhibited HB oxidation when added to liver slices prolonged hypnosis. In addition, 5'-AMP, adenosine, and cyclic guanosine 3',5'-monophosphate (cGMP) failed to alter HB biotransformation by liver slices. A similar pattern of impairment of metabolism by liver slices was observed when PCMA was used as the substrate. The inhibitory effect of DBcAMP was not altered by concurrent addition of either cGMP or DBcGMP. No impairment in the rate of microsomal PCMA biotransformation resulted from addition of adenosine or any of the nucleotides used in this study.