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Department of Biochemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada
(Received 14 September 1977)
It has been shown previously (Lyttle & Jellinck, 1972) that an enzyme that catalyses the binding of oestradiol-17β to protein in the presence of H2O2 is absent from the uteri of immature rats, but can be induced by physiological doses of oestradiol-17β or gonadotrophin. The induction of peroxidase in the rat uterus under various endocrine conditions has also been investigated (Jellinck & Newcombe, 1977a) and good correlation has been obtained between the ability of compounds to induce the enzyme and their oestrogenic activity (Jellinck & Newcombe, 1977b). In this paper we report on the activity of peroxidase in tissues other than the uterus and the effect of ovariectomy, hypophysectomy and treatment with oestradiol-17β on the levels of this enzyme.
Peroxidase was prepared from tissues of immature (26–29 days old) Holtzman rats weighing 70–90 g as described
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SUMMARY
Oestrone administered in the form of subcutaneous pellets produced marked changes in the metabolism of [14C]oestradiol by male rat liver microsomes. The high yield of both 2-hydroxyoestradiol and water-soluble metabolites was decreased to the level normally observed in females and this effect was induced by relatively small amounts of oestrogen within a few days after implantation. The action of testosterone on the hepatic metabolism of oestrogens was also investigated together with the effect of removing the hormone pellets at different time intervals. In addition, the rate of absorption of the steroids was determined by direct weighing and, in the case of oestrone, controlled by using radioactive pellets of known specific activity.
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It has been shown previously (Jellinck & Lucieer, 1965) that liver microsomes derived from male rats convert a higher proportion of [14C]oestradiol to its 2-hydroxy derivative and to water-soluble products than similar preparations from female rats. This sex difference in oestrogen metabolism could be altered by changing the hormonal environment; male rats acquired a female metabolic pattern when implanted with a pellet of oestrone (Jellinck & Woo, 1967). A number of natural and synthetic oestrogens in pellet form were therefore tested to determine whether they had the same action as oestrone on rat liver microsomes. The effect of structurally related non-oestrogenic analogues was also examined.
Compounds to be tested were compressed into cylindrical pellets (15–25 mg.) and implanted into adult male hooded or Sprague-Dawley rats. The dose released from the pellets is very small (e.g. < 50 μg. oestrone or stilboestrol/day, Jellinck & Woo, 1967). The animals were killed
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The inactivation of oestrogens in rat uteri was first studied by Lucas, Neufeld, Utterback, Martin & Stotz (1955) and later by Klebanoff (1965) who attributed the reaction to a peroxidase present in eosinophil leucocytes. These cells are not found in the uteri of immature animals but their flow to this organ is influenced markedly by the female sex hormones (Bjersing & Borglin, 1964; Ross & Klebanoff, 1966). More recently, it has been shown (Lyttle & Jellinck, 1972) that an enzyme which is absent from the uteri of immature rats can catalyse the metabolism and binding of [14C]oestradiol to protein in the presence of H2O2 in animals treated with physiological doses of oestrogen or gonadotrophin. Much of the evidence (Jellinck & Lyttle, 1973), coupled with the histochemical studies of Brökelmann & Fawcett (1969) points to the existence of a uterine peroxidase produced in situ distinct from the
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It has been shown (Noble & Graham, 1953; Graham, Beer & Noble, 1960) that pregnant mare serum gonadotrophin (PMS) loses its gonadotrophic activity on incubation with certain quinones. Since it is now well established that oestrogens are converted to 2-hydroxy metabolites by man and other species (Engel, Baggett & Carter, 1957; Kraychy & Gallagher, 1957; King, 1961) and since these might then be further oxidized to quinones, it was decided to investigate the effect of such orthohydroxylated steroids and their oxidation products on the inactivation of PMS.
Oestradiol-17β and 2-hydroxyoestradiol-17β were converted to their o-quinones with mushroom phenolase (Jellinck, 1960; Jellinck & Irwin, 1963). The PMS (150 i.u. in 3·3 mg.) dissolved in potassium phosphate buffer (0·067 m), pH 7·0, was incubated in O2 at 37° for 2 hr. with 1 mg. of phenolase (mushroom tyrosinase, grade II, Sigma Chemical Co.) and oestrogen (60 μg.); total volume, 3
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SUMMARY
The effect of age and the role of the pituitary and gonads on the change in liver oestrogen hydroxylase activity induced by oestrone and testosterone has been investigated. Testosterone increased the hydroxylation of oestradiol in immature rats but had no effect in adult female animals unless they had been ovariectomized. In male rats, hypophysectomy resulted in a rapid decrease in oestrogen metabolism which could not be reversed by treatment with testosterone. Oestrone produced reversible changes in oestrogen hydroxylation in adult male rats in contrast to the irreversible effects observed in immature animals. The significance of these results in the control of oestrogen metabolism is discussed.
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Department of Biochemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada
(Received 25 January 1977)
Previous studies (Lyttle & Jellinck, 1972) have shown that an enzyme that catalyses the binding of oestradiol to protein and other high molecular weight substances in the presence of H2O2 is absent from the uteri of immature rats, but can be induced by physiological doses of oestradiol or pregnant mare serum gonadotrophin (PMSG).
We now report the effect of oestradiol and PMSG administered in vivo on the induction of peroxidase in the uteri of rats under various endocrine conditions. The effects of oestradiol and progesterone on the formation of the uterine enzyme after a priming dose of oestrogen were also investigated.
Uterine peroxidase was prepared from immature (26-29 days old) Holtzman rats weighing 70-90 g as described previously (Lyttle & Jellinck, 1972) and assayed by its ability to convert [4-14C] oestradiol to water-soluble products in the
