The effect of delta 1-testolactone on serum testosterone and estradiol in the adult male rat

Estrogens inhibit angiotensin II-induced leukocyte-endothelial cell interactions in vivo via rapid endothelial nitric oxide synthase and cyclooxygenase activation

Angiotensin II (Ang II) may be a key molecule in the development of atherosclerosis. Because the incidence of coronary atherosclerosis in premenopausal women is lower than that observed in men or postmenopausal women, we have investigated the effect of estrogens on Ang II-induced leukocyte recruitment in vivo using intravital microscopy in the rat mesenteric microcirculation. Superfusion for 60 minutes with Ang II induced a significant increase in leukocyte rolling flux, adhesion, and emigration. Administration of 17-beta-estradiol (17-beta-E) after 30 minutes of Ang II superfusion produced a reduction of these leukocyte responses by 55.1%, 72.7%, and 70.9%, respectively, an additional 30 minutes later. The effect observed with 17-beta-E was receptor-mediated and specific. 17-beta-E superfusion did not modify either L-NAME or indomethacin-induced leukocyte responses. Inhibitory responses caused by 17-beta-E were not altered by either 7-nitroindazole or actinomycin D cosuperfusion. Stimulation of endothelial cells with 17-beta-E caused a rapid and dose-dependent release of prostacyclin. Finally, tamoxifen or ICI 182,780 administration provoked a significant increase in leukocyte-endothelial cell interactions 90 minutes later, which were significantly attenuated by systemic preadministration with an Ang II AT(1) receptor antagonist. Tamoxifen-induced leukocyte responses were also reduced by systemic pretreatment with an anti-P-selectin mAb and an anti-CD18 mAb. Hence, the antiatherogenic effects of estrogens may be mediated by inhibition of Ang II-induced leukocyte recruitment through endothelial NO and prostacyclin release. Furthermore, scarcity of estrogens resulted in decreased levels of vasodilators and the exposure of the endothelium to the deleterious action of Ang II, which may explain the higher incidence of coronary atherosclerosis in men and postmenopausal women.

Effects of gender and sex steroids on the immune response

Elevated immune responses and the higher incidence of autoimmune diseases in female (compared to male) humans and animals have been known for a long time. However, the scientific interest in this interrelationship has been limited both amongst immunologists and endocrinologists. It is mainly in the last ten years that investigations in this area have been intensifying. A number of fairly recent review articles confirm the increased interest in various aspects of this "interdiscipline" [1-4]. In the present paper we should like to make a new assessment of the state of knowledge. We shall firstly discuss heteroimmune response differences between males and females in humans, rodents and birds and then the roles of gender and sex hormones in autoimmune disease in various species. The general conclusions are the following. Gender and sex hormones have a clear effect on various hetero- and auto-immune responses but the mechanisms of action are still unknown; starting from sex hormones, steroids can be devised which have favourable effects on immune processes but lack undesirable hormonal effects; such hormonomimetics should be, in principle, applicable for the treatment of autoimmune disease.

Human trophoblast xenografts in athymic mice: a model for peripheral aromatization

A novel procedure was developed for evaluating aromatase inhibitors using human enzyme in a rodent model. Human choriocarcinoma trophoblast (JAr line) cells injected subcutaneously into athymic nude mice develop into tumor xenografts in 7-14 days which represent sites for peripheral aromatization of androgens. The rapid growth of these trophoblast tumors is estrogen independent. The tumors provide a source of nonovarian human tissue which has relatively high levels of enzyme activity (248 +/- 12 pmol estrogen/g/h) for biochemical determination of in vivo aromatase inhibition. These are major advantages for pharmacological evaluations in comparison to the slow tumor growth response of most carcinogen-induced rodent mammary cancers, which are usually devoid of aromatase activity. In addition, the hormonal dependent components of rodent mammary tumors require several weeks to regress as a result of the indirect effects of estrogen deprivation on tumor growth via inhibition of prolactin dependency, a minor component relative to the role estrogen occupies in hormonally-dependent breast cancer in humans. This model of peripheral aromatization was utilized to evaluate in vivo pharmacological parameters of MDL 18,962 (10-(2-propynyl)estr-4-ene-3,17-dione) such as bioavailability of several formulations, time course and dose responses following different routes of drug administration, pharmacokinetics and tissue distribution of [14C]MDL 18,962. Tumor aromatase activities of trophoblast xenografts were significantly (P less than or equal to 0.05) inhibited when MDL 18,962 was administered intravenously, orally, subcutaneously, or via subcutaneous silastic implants. The ED50 of MDL 18,962 for tumor aromatase inhibition at 6 h after a single treatment was 1.4 mg/kg, s.c. and 3.0 mg/kg, orally. MDL 18,962 blocked aromatase activity more effectively in human trophoblast than in mouse ovarian tissue. Human trophoblast aromatase activity was inhibited by 70% following a single oral dose of 100 mg/kg of MDL 18,962, while the host's ovarian aromatase activity exhibited only marginal inhibition. In vitro, the addition of 10 microM MDL 18,962 to trophoblast tumor cytosol or mouse ovarian cytosol resulted in 99.6 and 91.4% inhibition of aromatase activity, respectively. Tissue distribution of [14C]MDL 18,962 was predominantly associated with endocrine tissues with aromatase activity and organ systems involved in steroid metabolism and excretion. These in vivo data show that MDL 18,962 an enzyme-activated aromatase inhibitor, causes prolonged aromatase inhibition in the absence of saturating levels of inhibitor.

Effect of aromatase inhibition by delta 1-testolactone on basal and luteinizing hormone-releasing hormone-stimulated pituitary and gonadal hormonal function in oligospermic men

Aromatase inhibition by delta 1-testolactone (TL), 500 mg twice daily for 4 weeks, in nine patients with idiopathic oligospermia lowered circulating estradiol (E2) levels by about 30%, enhanced the secretion of follicle-stimulating hormone (+ 30%), 17-hydroxyprogesterone (17-OHP) (+ 40%), and testosterone (T) (+ 30%), but did not affect serum luteinizing hormone levels. Despite E2 lowering, there was an accumulation of 17-OHP over T, suggesting 17, 20-lyase inhibition. Unexpectedly, administration of TL almost completely deleted the T response to continuous luteinizing hormone-releasing hormone infusion present before TL therapy, despite similar gonadotropin release. Because the 17-OHP response to the luteinizing hormone-releasing hormone infusion was even higher during therapy, the 17,20-lyase lesion seemed aggravated despite substantial reduction of E2 levels. Although the present data suggest that estrogens play a less dominant role in the origin of the late steroidogenetic lesion than previously assumed, the suggestion also arises that TL per se, in addition to its antiestrogenic action, exerts an inhibiting effect on the 17,20-lyase locus, which may obscure the beneficial effect of reducing E2.

Short-term effects of testolactone on human testicular steroid production and on the response to human chorionic gonadotropin

Testicular responsiveness to a single dose of human chorionic gonadotropin was studied in five normal men before and during short-term treatment with an aromatization inhibitor, testolactone (TL). TL alone resulted in significant increases in the serum concentrations of progesterone, 17-hydroxyprogesterone, 17-hydroxypregnenolone, dehydroepiandrosterone, androstenedione, and the sulfate conjugates of pregnenolone, 17-hydroxypregnenolone and testosterone (T). Concentrations of 5-androstene-3 beta, 17 beta-diol and T remained unchanged, and those of estradiol (E2) decreased. TL had no major influence on serum luteinizing hormone, follicle-stimulating hormone, prolactin, or sex-hormone-binding globulin concentrations. During TL administration, human chorionic gonadotropin stimulation led to a significantly decreased E2 response, but the T response was unchanged. Alleviation of an inhibitory influence of E2 on the steroidogenic enzymes, especially 17,20-desmolase, was probably the reason behind the increased synthesis of several T precursors. In addition, TL appeared to have an inhibitory influence on the 17 beta-reduction of T precursors. TL resulted in increased serum concentrations of some steroid sulfates, but the mechanism of this effect remains unclear.