Endocrine regulation of the metabolism of 1-naphthol in the rat.

A sex difference exists in the rate of conjugation of 1-naphthol by rat liver cubes with the male exhibiting a more than 3-fold higher activity (1.69 +/- 0.20 and 0.48 +/- 0.04 nmol of conjugate formed per min/g of liver in male and female, respectively). Hypophysectomy reduced the conjugating activity in both male and female rats (by 57% in the male and 42% in the female). Thyroidectomy also decreased the rate of conjugation in both sexes and adrenalectomy was without effect. Castration of the male animals caused a significant reduction in activity (of 32%) but ovariectomy resulted in a marked increase in conjugation (of 60%). The effect of hypophysectomy in the male can therefore be explained in terms of the hypophyseal control of the thyroid gland and testes but the effect of pituitary ablation in the female is more difficult to explain in terms of interference with peripheral endocrine organs as hypophysectomy and ovariectomy have such opposite effects. The effect of ovariectomy is seen to be reversed by estradiol benzoate treatment and testosterone has a small effect in the castrated but not the hypophysectomized male animals. This indicates that estrogens and androgens are important regulators of 1-naphthol conjugation and that androgens probably act via the hypothalamo-pituitary axis and not directly on the liver. This is substantiated further by the partial reversal of the effect of hypophysectomy by a renal pituitary implant or growth hormone. The conjugate formed from 1-naphthol is seen to be all glucuronide and this is unaffected by the sex of the animal or by hypophysectomy.(ABSTRACT TRUNCATED AT 250 WORDS)