Brief maternal deprivation of rats reduces hepatic mixed function oxidase activities.

Deprivation of pups from mother and sibs for 3 min daily from day 5 to day 41 of life reduced activities of 4 hepatic mixed function oxidases (MFO) expressed per mg protein in male rats compared to unhandled control rats. These decreases, though generally small, 22.4% and under, reached statistical significance for the substrates aminopyrine, benzphetamine and ethoxycoumarin. This handling procedure did not consistently affect the inductive response to phenobarbital. Previously ignored as a source of variability in response to xenobiotics, "handling" appears from these results to merit further investigation as such a factor in uninduced rats. Differences among rats in "handling" could contribute to large day-to-day variations in their metabolism of xenobiotics.