The target cell responses to steroid hormones, such as oestrogens, are dependent on the expression of their receptors. Apart from receptor concentration, another key regulatory factor in steroid hormone action is the intracellular hormone concentration, which is affected by three main variables: the concentration of the steroid in plasma, local production and local conversion into metabolites. During the reproductive years the main source of oestrogens is the ovarian follicle, but in postmenopausal women most of the oestrogens are formed in peripheral tissues. The present overview deals with the formation of active oestrogens in steroidogenic tissues and in oestrogen target tissues, and the main focus is on 17β-hydroxysteroid dehydrogenases, which catalyse the interconversion between oestradiol and oestrone. It is evident that different 17β-hydroxysteroid dehydrogenase isoenzymes are responsible for the oxidation/ reduction of oestradiol or oestrone in oestrogen target cells. Because these enzymes are involved in the biosynthesis and metabolism of oestrogens, they have an important physiological significance for the growth of oestrogen-dependent tissues and, hence, the growth and progression of hormone-dependent tumours.
LH recepto rs, cAMP production and steroidogenesiswere compared in the human and rat testis in vitro,using whole tissue preparations and interstitial cell suspensions.Human testis tissue was obtained from prostatic cancer patientsundergoing orchiectomy (mean age, 71.6 yr); rat testis tissue wasfrom 80- to 90-day-old animals. The amount of [125I]iodohCGbinding in human testis homogenates averaged 0.57 ± 0.14 nmol⁄g wet wt (SE; n = 13), and the number of binding sites per Leydigcell was 1630 ± 220 (n = 5). In the rat, a similar calculation gave23,500 ± 2,500 (n = 4) binding sites per Leydig cell. The equilibriumassociation constants (Kas) of hCG binding to the humanand rat Leydig cell suspensions were 1.4 and 2.9 X 1010 M-1,respectively. Basal cAMP production in the human testis tissuewas 729 ± 225 pmol⁄g 4 h (n= 4), and maximal hCG stimulation(2 X 10-9 M) increased it on average by 590%. The basal rate ofcAMP production in the rat testis tissue was 59 ± 4.0 pmol⁄g 4h (n = 5), and hCG stimulated this rate by 1,030%. Basaltestosterone (T) production in the human testis tissue was 4.4± 0.7 nmol⁄g. 4 h (n = 15), but the hCG stimulation was only 44± 11% (P < 0.02). Similar rates of hCG stimulation were seen inthe production of pregnenolone, progesterone, and 17-hydroxyprogesterone(P < 0.01–0.05). In the rat testis, the basal Tproduction was 0.54 ± 0.10 nmol⁄g 4 h, and gonadotropinstimulation of T production was as high as 5- to 6-fold. TheED50s of hCG-induced production of T and cAMP, measured inLeydig cell suspensions, were similar in both species, on theorder of 1 pM for T and 100 pM for cAMP. In interstitial cellsuspensions, the rates of stimulation of cAMP production in therat and of T production in both species were comparable withthose observed in whole tissue preparations. However, the hCGstimulation of human Leydig cell cAMP production was only 2-fold. It is concluded that human Leydig cells, in comparison withthose of the rat, have a low amount of LH receptors (less than10%). When corrected for the differences in Leydig cell proportionof the tissue, the basal rates of T and cAMP productionwere similar in the tissue pieces of both species. Gonadotropinstimulation increased human testicular steroidogenesis onlymarginally (less than 50%), in contrast to a 5- to 17-fold increasein the rat. The cAMP production was stimulated by hCG 7- to10-fold in both species studied. The low level of acute stimulationof human testicular steroidogenesis was localized to a metabolicstep beyond LH receptors and cAMP formation but beforefurther metabolism of pregnenolone, being most likely due to aninsufficient supply or further metabolism of mitochondrial cholesterol.(Clin Endocrinol Metab55: 882, 1982)
The inhibitory effects of recombinant porcine interferon-γ (IFNγ) on human CG (hCG)-stimulated testosterone production, and on mRNA concentrations of cholesterol side-chain cleavage (P450scc) and 17α-hydroxylase/C17-20lyase (P450c17) were investigated using porcine primary Leydig cell culture as a model. After preincubation of Leydig cells for 24 h with 1000 pM IFNγ, hCG-stimulated (10 ng/ml, 2 h) testosterone production was inhibited by 50%, whereas no significant changes were seen in hCGstimulated cAMP production. Incubation with 10 μM 5-cholestene-3β,22(R)-diol or 10 μM 5-cholestene-3β,2Oα-diol together with hCG (10 ng/ml, 2 h) reversed most of the inhibitory effect of IFNγ, suggesting that IFNγ inhibits P450scc activity, possibly by inhibiting the substrate (cholesterol) availability for P450scc. Incubation with IFNγ also decreased basal concentrations of P450scc (45%) and P450c17 (35%) mRNA, although these changes probably did not contribute to the decreased testosterone production. Long-term treatment with hCG (100 ng/ml, 24 h) increased P450scc mRNA (3- to 4-fold) and P450c17 mRNA (4- to 5-fold) concentrations. Simultaneous treatment with IFNγ attenuated these hCGinduced increases in P450scc mRNA (50%) and P450c17 mRNA (40–100%) concentrations, as well as in testosterone production (77%). This inhibition of testosterone production could only be partly reversed by the hydroxylated cholesterol derivatives. This suggests that in addition to possible suppression of cholesterol availability, decreased P450scc and/or P450c17 activities (through decreased mRNA concentrations) were also involved in the IFNγ suppressed steroidogenic capacity of porcine Leydig cells during long-term hCG stimulation.
Cyproterone acetate (100 mg daily on the 5th-14th days of the normal cycle) together with ethinyl estradiol (0.05 mg daily on the 5th-25th days) was used for the treatment of hirsutism in 23 women for six months. This treatment caused a significant decrease in the severity of the hirsutism after only three months, the effect being maximal after six months. Sixty per cent of our patients reported being subjectively satisfied with the results. A relapse occurred, however, within three months of the end of the treatment in half the patients. The serum testosterone was significantly decreased after three months of treatment, but the changes in serum testosterone did not follow the changes in the clinical picture of hirsutism, suggesting that one facet in the favorable action of cyproterone acetate is an inhibition of the action of androgen on target cells. Various side effects, such as nausea, headache, loss of libido and depression, were reported very frequently, which undoubtedly limits the large scale use of this treatment, at least with the doses used in this study.
Specific high affinity, low capacity binding of [l25I]iodo-hCG was demonstrated in homogenates of isolated granulosa cells and corpora lutea of human ovary throughout the menstrual cycle and pregnancy. The binding of radiolabeled hCG to the receptor was time, temperature, ion concentration, and pH dependent. The treatment of ovarian membrane particles with trypsin decreased binding by about 75%, whereas treatment and neuraminidase resulted in a 400% increase in binding. These results suggest a protein nature of the receptor and that a portion of the receptors may be masked in the membrane by sialic acid. The receptor displayed high specificity for hCG and human LH, indicating that they share the same receptor site in the human ovary. The receptor bound hCG with high affinity. The apparent equilibrium association constant for hCG was 2.2 × 109 M-1 The receptor concentration increased from the early follicular phase to ovulation by about 1.6-fold. After an apparent transient fall associated with the ovulatory period, the receptor concentration increased further by about 4-fold by day 17 of the cycle and thereafter remained virutally unchanged until the end of the cycle. Homogenates of corpora lutea obtained during the follicuar phase aso bound specifically radiolabeled hCG, suggesting that the regression of the corporalutea is not primarily due to the loss of receptors for human LH. The receptor concentration measured in corpora lutea of early pregnancy was clearly lower than that in corpora lutea of the menstrual cycle. This is most likely due to occupation and downregulation of the receptors by high serum hCG. The number of receptors in corpora lutea tended to increase towards the end of pregnancy. Our results indicate that the maturation and subsequent luteinization of human ovarian follicles is associated with a biphasis increase in the number of LH (hCG) receptors in granulosa cells. The changes in the concentration of available receptor may have a determining role in the regulation of follicular and corpus luteum development and function. (J Clin Endocrinol Metab108: 307, 1981)
The biological effects of a new synthetic progestagen, Org 2969 (13-ethyl-11-methylene-18,19-dinor-17 alpha-pregn-4-en-20-yn-17-ol) were studied in healthy normally menstruating women. Two of them were given 0.125 mg, five 0.060 mg and two 0.030 mg of Org 2969 daily on days 1-20 during one menstrual cycle. Serum levels of follicle stimulating hormone, luteinizing hormone, progesterone and oestradiol were analyzed on days 8-23 in order to evaluate the function of the hypophyseal-ovarian axis. The serum concentrations of aspartate amino transferase, alanine amino transferase, alkaline phosphatase, gamma glutamyl transpeptidase and bilirubin were determined to evaluate possible side effects on live function on days 8, 15 and 23. Serum cortisol was measured on days 8 and 23. The basal body temperature was recorded daily during the whole cycle, and endometrium biopsies were taken on days 21 or 22 of the cycle. All samples were taken similaryl during the treatment cycle and the preceding control cycle. According to the hormone determinations, all the treatment cycles were anovulatory except in one woman receiving the lowest dose. The treatment led to decreased spinnbarkeit, arborization and sperum penetration in the cervical mucus. Liver function tests and serum cortisol remained unchanged during the treatment.
