Role of albumin in the biotransformation of biphenyl by isolated rat hepatocytes

: The role of albumin in biotransformation of biphenyl, a lipophilic xenobiotic, by isolated rat hepatocytes has been studied. It is shown that in the absence of albumin biphenyl is quickly and almost completely bound by cells. The rate of formation of 4-hydroxybiphenyl, the reaction product, depends on the substrate concentration (in the range 8.5-70 microM) and conforms with the Mikhaelis-Menten equation. An increase in the biphenyl concentration in the incubating medium to 140 microM induces no changes in the rate of its biotransformation. Serum albumin, while binding biphenyl, also reduces its effective concentration in a cell, which prevents the cytochrome-P-450-dependent monooxygenase system of hepatocytes from the inhibiting effect of high concentrations of the xenobiotic.