Phase difference in the induction of tyrosine hydroxylase in cell body and nerve terminals of sympathetic neurones

The induction of tyrosine hydroxylase in the nerve terminals of the rat heart by reserpine lags behind that in the stellate ganglion by two to three days. Cycloheximide given three days after reserpine blocks the further rise of the enzyme in the nerve terminals. The increase in tyrosine hydroxylase activity of the lumbar ganglion is as marked as that in the stellate ganglion. The increase of enzyme activity in the sciatic nerve after reserpine administration resembles that found in the heart nerve terminals. Determination of enzyme activity in segments of sciatic nerves indicates a two-day lag and then a proximal-distal transport of enzyme, but the apparent rate is not sufficient to account for the increase in enzyme in the nerve terminals. These findings are compatible with the local synthesis of induced tyrosine hydroxylase in the nerve terminals rather than the peripheral movement of the completed enzyme.

Enzymatic hydroxylation of benzopyrene and its relationship to cytotoxicity

Aryl hydrocarbon hydroxylase, an inducible microsomal enzyme system, has been measured in cultures of normal and transformed hamster, mouse, and human cells. In order to determine the highest level of enzyme, the cells were induced by pretreatment with benz(a)anthracene. A correlation was found between the level of enzyme activity and the susceptibility of the cells to the cytotoxicity produced after treatment with benzopyrene. The results indicate that aryl hydrocarbon hydroxylase is the enzyme system responsible for cell susceptibility to the cytotoxic effect of benzopyrene and the toxic effect of benzopyrene is due to its enzymatic conversion to a cytotoxic metabolite. 3-Hydroxybenzopyrene, one of the products of the enzymatic hydroxylation of benzopyrene, was found to be cytotoxic to cells that were either susceptible or resistant to the cytotoxic effect of benzopyrene.

Hepatic microsomal enzymes in man and rat: induction and inhibition by ethanol

The feeding of ethanol increased significantly the activities of hepatic pentobarbital and benzpyrene hydroxylases in rats, and, in human volunteers, doubled pentobarbital hydroxylase activity. In vitro ethanol inhibited aniline, pentobarbital, and benzpyrene hydroxylases. These data may explain, at least in part, the increased tolerance of alcoholics to sedatives when sober, and the enhanced sensitivity to sedatives when inebriated.

Benzpyrene hydroxylase induction by polycyclic hydrocarbons in hamster embryonic cells grown in vitro

Treatment of hamster embryonic cells with 1,2-benzanthracene for 4 to 48 hours induced a three- to tenfold increase in the activity of benzpyrene hydroxylase. That the increase in enzyme activity was completely prevented by puromycin suggested an induction of enzyme synthesis.