lhrh--n-ac-2-nal(1)-4-cl-phe(2)-trp(3)-hci(6)-alanh2(10)- and Body-Weight

Premenopausal women have a lower risk of coronary artery disease than men or postmenopausal women; estrogens are thought to contribute to this lower risk. Administration of exogenous estrogen to post-menopausal women increases plasma high density lipoprotein (HDL) cholesterol and may reduce mortality from coronary disease in users. Although many investigations have examined the roles of estrogen in the regulation of lipoproteins in women, little attention has been directed to estrogen regulation of lipids in men. We designed a paradigm to study the role of physiological levels of estradiol (E2) on plasma lipoproteins in healthy men. We used a GnRH antagonist, Nal-Glu, to suppress endogenous steroid hormones in healthy men. We then administered testosterone (T) enanthate (100 mg, im, weekly) to restore T levels to the baseline range, and we administered an aromatase inhibitor, testolactone (Teslac), to prevent the normal conversion of T to E2, thereby producing a selective estrogen deficiency state in normal young men. As controls, we administered Nal-Glu and T along with placebo Teslac to a separate group of men; a third group of men received all placebo medications. We found that in men who received Nal-Glu plus T plus Teslac, E2 levels were profoundly suppressed during treatment, whereas T levels remained in the baseline range. Plasma HDL cholesterol, particularly, the HDL2 fraction, decreased significantly in response to the low serum E2 level. Plasma apoprotein-AI levels also decreased significantly. Plasma LDL and triglyceride levels did not change. All hormone and lipoprotein parameters returned to baseline within 4 weeks after treatment ended. In men who received Nal-Glu plus T, plasma HDL and apoprotein-AI decreased, but these decreases did not achieve statistical significance. Only a small decrease in HDL2 cholesterol was seen in these men. There were no hormonal or lipid changes in the placebo group. We conclude that in men, physiological levels of E2 are important in maintaining plasma levels of HDL cholesterol, especially the HDL2 fraction. These observations suggest that estrogen, in the amount normally produced in men, may offer some degree of protection against cardiovascular disease in males, as they do in women.

Topics: Adult; Apolipoprotein A-I; Body Weight; Cholesterol, HDL; Cholesterol, LDL; Dose-Response Relationship, Drug; Estradiol; Gonadotropin-Releasing Hormone; Humans; Male; Testolactone; Testosterone; Triglycerides

The effects of gonadotropins and gonadal steroids on androgen-binding protein (ABP) production and its distribution among the epididymis, seminiferous tubule fluid (STF), testicular interstitial fluid (TIF), and blood were studied in 300-g adult male Sprague-Dawley rats. The rats either received no treatment or their pituitary function was suppressed by administration of the GnRH antagonist [AcD2Nal,D4ClDPhe2,D3Pal3,Arg5,DGlu6 (AA),D-Ala10]LHRH (antagonist). Other groups of rats were treated with hCG, FSH, FSH plus hCG, testosterone, or estradiol, alone or together with antagonist. Treatment was conducted for 30 days, after which time, ABP was detected by its ability to bind [3H]5 alpha-dihydrotestosterone. Transport of ABP from the testis to the epididymis was inhibited by antagonist administration. Simultaneous treatment with antagonist and hCG, or antagonist and hCG plus FSH prevented antagonist-induced inhibition of ABP transport. Neither FSH, testosterone, nor estradiol alone was effective in this process. Inhibition of ABP transport to the epididymis was accompanied by its accumulation within the testis. Treatment with antagonist and FSH resulted in a 4.5-fold increase in the concentration of ABP in TIF, but had little effect on the amount of ABP in STF, indicating selective secretion of ABP from the basal surface of the Sertoli cells. Treatment with antagonist alone, antagonist together with testosterone or estradiol, or estradiol alone resulted in increased concentrations of ABP in both TIF and STF, but the increase in TIF was proportionately greater. Treatment with hCG or FSH plus hCG alone or with antagonist not only facilitated ABP transport to the epididymis, but also increased TIF levels of ABP above control values. The former treatment resulted in increased concentrations of testosterone in TIF, but not in STF. Both treatments resulted in testosterone levels in both compartments that were higher than those in animals treated with antagonist alone. No treatment had a statistically significant effect on blood levels of ABP. About 50% of ABP synthesis appears to be constitutive, i.e. is not regulated by hormones. Although ABP production continues in the presence of antagonist, its transport to the epididymis is halted, indicating that epididymal transport of ABP is a hormone-dependent process. It is likely that elevated intratesticular levels of testosterone or FSH and testosterone acting in concert regulate epididymal transport of ABP.

Topics: Androgen-Binding Protein; Animals; Body Weight; Chorionic Gonadotropin; Epididymis; Estradiol; Extracellular Space; Follicle Stimulating Hormone; Gonadotropin-Releasing Hormone; Male; Organ Size; Pituitary Gland; Rats; Rats, Sprague-Dawley; Seminiferous Tubules; Testis; Testosterone

[Ac-D2Nal1,4Cl-DPhe2,D3Pal3,Arg5,DGlu6+ ++ (anisole adduct),DAla10]-GnRH (Nal-Glu) is an antagonist of LHRH and has the potential to be utilized as an antigonadal agent. A study was undertaken to evaluate the toxicological effects of Nal-Glu in rats. Nal-Glu, dissolved in 5% mannitol in water containing 9 ml/liter benzyl alcohol, was administered subcutaneously. In subchronic studies, groups of 12 male and 12 female rats received 0, 50, 250, or 1250 micrograms/kg body weight (BW) Nal-Glu for 90 days and were killed on Day 91. Additional groups of male and female rats were given the high dose of Nal-Glu (1250 micrograms/kg BW) or vehicle for either 30 or 90 days. Their fertility was assessed by mating them with normal animals. Unlike some other LHRH antagonists, Nal-Glu exhibited a low potency for causing in vitro histamine release from rat peritoneal mast cells. Furthermore, in acute in vivo studies, Nal-Glu was less active in the induction of peripheral edema. In the subchronic study, all doses of Nal-Glu were well tolerated and there were no apparent systemic toxic effects. The pharmacological effects of Nal-Glu were quite evident, however. Nal-Glu treatment led to a significantly decreased body weight gain in the males and a significantly increased body weight gain in the females. There was a dose-dependent decrease in weights of gonads and reproductive organs in both the sexes. Some of the hematological and serological parameters were significantly different in Nal-Glu-treated animals. However, most of the values were within the normal range and are considered to be of no toxicological significance. Histopathological evaluations were made in the control and high-dose groups only. In the male, a seminiferous tubular degeneration and atrophy of the interstitial cells was seen. The prostate and seminal vesicles were also atrophied and the epididymides were devoid of spermatozoa. In the females, the ovaries and uteri were atrophic. The injection site of Nal-Glu-treated rats had inflammatory changes indicative of a local irritating action of the drug. All other tissues had normal histomorphology. Both male and female rats became infertile when 1250 micrograms/kg Nal-Glu was administered for 30 days. Normal fertility was restored 8 weeks after cessation of 90-day treatment. It is concluded that repeated administration of Nal-Glu leads to reversible infertility in both male and female rats. Although it was irritating at the site of injection. Nal-Glu had no

Topics: Animals; Atrophy; Body Weight; Dose-Response Relationship, Drug; Female; Fertility; Follicle Stimulating Hormone; Gonadotropin-Releasing Hormone; Hematocrit; Histamine; Histamine Release; Injections, Subcutaneous; Luteinizing Hormone; Male; Rats; Rats, Inbred Strains; Testis; Testosterone