Cytoplasmic progesterone receptors in uterine tissue of the snapping turtle (Chelydra serpentina).

A high affinity progesterone-binding component was detected in the cytosol of the uterus of the snapping turtle, Chelydra serpentina. Density gradient centrifugation indicated that binding of [3H]progesterone and [3H]promegestone (R5020) was to a fraction with a heavier sedimentation coefficient than bovine serum albumin (BSA) appearing as a broader peak in the 6-7 S region; it was not affected by excess cortisol. Another binding peak, lighter than BSA and appearing with [3H]R5020 and [3H]progesterone near the 4 S region, was affected by excess cortisol. Excess progesterone decreased both the heavier and lighter peaks. Analysis of steroid specificity revealed that, of the natural steroids, progesterone had the highest affinity for the uterine cytosol. This was followed by deoxycorticosterone, 5 alpha-pregnanedione, testosterone, oestradiol-17 beta, corticosterone, 5 alpha-dihydrotestosterone and cortisol. Non-linear regression analysis of saturation data indicated the presence of two classes of high affinity binding sites: progesterone-binding sites (R-sites) with equilibrium association constants (Ka) of 2.9 +/- 0.28 litres/nmol (mean +/- 95% confidence limit) for [3H]R5020 and 0.34 +/- 0.20 litres/nmol for [3H]progesterone, and corticosteroid-binding globulin-like sites (G-sites) with Ka of 4.5 +/- 1.6 litres/nmol for progesterone. The concentration of R-sites was between 0.66 +/- 0.10 and 2.6 +/- 0.55 pmol/mg protein while that of G-sites was between 0.73 +/- 0.05 and 5.0 +/- 0.27 pmol/mg protein. DEAE-cellulose filtration assay also confirmed the presence of R-sites and G-sites in the cytosol. R-sites were detectable without oestrogen priming during the preovulatory and vitellogenic phases (low progesterone, high oestrogen concentrations) when the ovarian follicles are mature (18-22 mm diameter).(ABSTRACT TRUNCATED AT 250 WORDS)

Binding of 5 alpha-dihydroprogesterone and other progestins to female rat anterior pituitary nuclear extracts.

The specific binding of 5 alpha-dihydroprogesterone (5 alpha-DHP), progesterone and R5020 to anterior pituitary nuclear extracts was studied using ovariectomized rats treated with estradiol benzoate and progesterone. The binding equilibrium association constant for 5 alpha-dihydroprogesterone with different preparations of nuclear extract ranged from 4.0 +/- 0.54 microM-1 to 59 +/- 10 microM-1. The association constants for progesterone and R5020 were 0.39 +/- 0.81 nM-1 and 1.5 +/- 0.15 nM-1, respectively. The binding of 5 alpha-DHP was specific in that it could be competed only by R5020, progesterone and 5 alpha-DHP and not by other progesterone metabolites and other hormonal steroids tested. With [3H]-progesterone and [3H]R5020 as ligands the most efficient competitors also were R5020, progesterone and 5 alpha-DHP. Estrogen priming of ovariectomized rats consistently and significantly increased the number of binding sites for all three progestins and subsequent progesterone treatment enabled their detection at higher levels in the nuclei.

Progesterone-induced glycogen accumulation in human endometrium during organ culture.

An organ culture system was used to evaluate the response of human proliferative endometrium to progesterone stimulation. The glycogen content of proliferative tissue was increased as much as thirteenfold during organ culture in media containing progesterone. The steroid-induced increase in tissue glycogen was detectable after 16 hours and reached a maximum at 48 and 72 hours of culture. Progesterone induced a significant increase in glycogen at a media concentration of 1.6 x 10(-8)M and a maximal increase at 3.2 x 10(-7) to 3.2 x 10(-6)M. At higher media concentrations of progesterone (1.6 x 10(-5)M), glycogen levels failed to reach the maximum obtainable. The extent of the response correlated poorly with the initial glycogen content of the tissue and not at all with the initial content of high-affinity progesterone-binding sites in cytosol. Addition of estradiol-17 beta to medium (10(-10)M to 10(-7)) has no effect on the progesterone-induced increase in tissue glycogen. Delaying the addition of progesterone to the cultures for 24 hours resulted in a diminished glycogen response; the reduced response may be related to a rapid decrease in high-affinity progesterone-binding sites as measured in cytosol prepared from tissues cultured in the absence of progesterone. High-affinity progesterone-binding sites in endometrial cytosol were found to decrease rapidly during the first 24 hours of culture. The addition of cycloheximide or actinomycin D to the culture media inhibited the increase in tissue glycogen caused by progesterone. These results demonstrate that progesterone can induce an in vitro response in human proliferative endometrium similar to that seen in vivo. The response of the endometrium is reproducible and allows for comparisons between grouped data obtained by using tissues from several different donors.

Synthetic progestins: in vitro potency on human endometrium and specific binding to cytosol receptor.

The relative potency of six commonly used synthetic progestins has been evaluated in an organ culture system for human endometrium. The affinities of these progestins for endometrial progesterone receptor were also evaluated after removing the CBG-like protein by spheroidal hydroxylapatite chromatography. All six progestins induced an increase in tissue glycogen during culture at lower concentrations than did progesterone; only one (medroxyprogesterone acetate) had a relative affinity greater than progesterone. The relative potencies and affinities of the synthetic progestins were found to have the same relative order but to differ in relative magnitude.

Cholesterol side chain cleavage and aromatase activities in the corpus luteum of the pregnant rhesus monkey.

Cholesterol side-chain cleavage (CSCC) and aromatase activities were measured in luteal mitochondria and tissue pieces, respectively, from rhesus monkeys on days 22, 49, 128 and 160 of gestation. CSCC activity did not vary significantly during gestation and thus probably does not respond to chorionic gonadotropin which is elevated on day 22 of pregnancy. It is not known, however, whether CSCC can be stimulated prior to day 22 when the corpus luteum is steroidogenically more active. Both 3H-pregnenolone and 3H-progesterone were synthesized from [1,2-3/]cholesterol. Aromatase activity declined from high levels on days 22 and 49 to a nadir on day 128 of pregnancy. Utilizing either [1beta-3H]androstenedione or [1beta-3H]testosterone as substrate yielded comparable results throughout gestation.

Placental and luteal steroidogenesis in the pregnant rhesus monkey.

Progesterone, 20alpha-dihydroprogesterone, estrone and estradiol-17beta concentrations were estimated by radioimmunoassay in blood plasma from uterine, uteroovarian and femoral veins of rhesus monkeys (Macaca mulatta) on days 22, 49, 128 and 160 of gestation. Steroids were consistently more concentrated in uterine and uteroovarian that in femoral venous plasma and in many cases levels in the uteroovarian vein were also higher than those in the uterine vein indicating luteal secretion of both progestins and estrogens thoughout gestation. In some animals, however, the corpus luteum appeared quiescent. As reflected in the decline in the uterine venous progesterone/estradiol-17beta concentration ratio, a shift in steroid contribution from the uterus and its contents occurred between days 22 and 49 of gestation with progesterone declining more rapidly than estradiol-17beta. Progesterone/20alpha-dihydroprogesterone was higher in both uterine and uteroovarian than in femoral venous plasma suggesting peripheral metabolism of progesterone to 20alpha-dihydroprogesterone.

Binding of progesterone by human uterine cytosol.

Progesterone binding by 100,000 X g cytosols of human myometria from patients undergoing hysterectomy for various reasons was assayed using equilibrium dialysis or DEAE-cellulose filtration. The estimates of high-affinity porgesterone binding obtained by both techniques showed a significant correlation. Dialysis and filtration assays with cortisol competing with [3H]progesterone for binding indicated that the specific progesterone binding by the cytosols was the result of progesterone interaction with two high-affinity constitutents. Myometrial cytosols from tissues under progestin stimulation (secretory endometrium or pregnancy) had low concentrations of progestin binders. Cytosols from uteri with atrophic endometrium showed consistently high concentrations of progestin binders and those tissues under estrogen stimulation (proliferative endometrium or hyperplasia) and variable binder concentrations. No differences were detected between grouped observtions classified into 10 clinical categories. The DEAE-cellulose filtration is an effective method for evaluating progesterone binding which uses well-established statistical techniques and requires less tissue, less time for incubations, and fewer points for reliable analysis than does equilibrium dialysis.

Binding of progesterone by human uterine cytosol.

PIP: Equilibrium dialysis or DEAE-cellulose filtration was employed to measure progesterone binding by 100,000 X g supernatants of human myometria from patients undergoing hysterectomy. A significant (p less than .01) correlation in the estimation of high-affinity progesterone binding was found for both techniques. When cortisol competed with tritiated-progesterone for binding receptors, dialysis and filtration assays indicated that the specific binding of progesterone by the cytosols was due to the interaction of progesterone with 2 high-affinity constituents. Cytosols under progestin stimulation had low concentrations of progestin binders, while those under estrogen stimulation had variable binder concentrations. Cytosols from uteri with atrophic endometrium had consistently high concentrations of progestin binders. The experiments showed DEAE-cellulose filtration to be an effective method for evaluating progesterone binding and requires less tissue, less time for incubation, and fewer points for reliable analysis than equilibrium dialysis.^ieng

A simple algorithm for the solution of the 'n X m' case of a binding equilibrium.

Accurate estimates of the equilibrium concentrations in the non-interactive reaction of several ligands with several classes of binding sites with univalent stoichiometry can be rapidly obtained by a simple method of successive approximations on a programmable desk calculator.

Hepatic hydroxylation of 3beta-hydroxy-5-androsten-17-one in orchiectomized or adrenalectomized rats exposed to a reversed light cycle, constant light, or constant darkness.

The oxidative metabolism of 3beta-hydroxy-5-androsten-17-one (DHA)2 by liver microsomes in vitro was studied in sham-operated, castrated, or adrenalectomized rats maintained for 21 days in a normal light cycle, a reverse light cycle, constant light, or constant darkness and killed either at 0600 or 1800 h. Statistical analysis of the data (3-way analysis of variance) indicated the following significant effects: 1) exposure to a reverse light cycle resulted in lower body weights and increased rates of formaation of 7alpha-OH-DHA and 7-oxo-DHA; 2) despite an increase in microsomal protein content, livers from rats in constant light had the lowest rates of formation of all DHA products; 3) rats kept in constant darkness exhibited the highest rates of DHA metabolism; 4) castration decreased the microsomal protein content and the rates of formation of 16alpha-OH-DHA, 7alpha-OH-DHA, and 7-oxo-DHA; 5) adrenalectomized rats exhibited high rates of 7alpha-OH-DHA formation although microsomal protein and liver and body weights decreased; and 6) the formation of 7-oxygenated products of DHA was greater in the rats killed at 1800 than at 0600 h. We conclude that the type of illumination is quantitatively more important in determining the magnitude of DHA metabolism by the adult male rat liver than either the adrenals or the testes.

Influence of adrenalectomy, castration, and light cycle on steroid hydroxylase activity in the adult male rat liver.

The contribution of the adrenals, the testes, and a light/dark cycle to the regulation of hepatic steroid hydroxylases was studied in vitro by measuring transformation rates (nmol/mg protein/min) of dehydroepiandrosterone (DHA). Normal and adrenalectomized male rats were kept in 12 h light:12 h dark (12L:12D) or in constant light (CL) for 1 week. Normal and castrated rats were kept in 12L:12D for 3 weeks. Rats were killed at 4-h intervals over a 36-h period, hepatic microsomal fractions were incubated with [4-14C]DHA, and C-7 and C-16-oxygenated products were quantitated. The overall mean rate of 7alpha-hydroxylation decreased in normal rats exposed to CL. Rates of both 7alpha- and 16alpha-hydroxylation were significantly greater in normal rats than in the respective group of treated rats, except for the 7alpha-hydroxylase in castrated rats. These results indicate that 16alpha-hydroxylase activity is both gonadal- and adrenal-dependent, whereas 7alpha-hydroxylase activity is adrenal-dependent only. Both enzymes are sensitive to light/dark modulations, although a circadian rhythm could not be conclusively established.

Aromatizing activity of placental microsomal fractions from ewes in late gestation.

Placental microsomes from eight domestic sheep at 136-146 days of gestation were incubated with radioactive androstenedione, testosterone and dehydroepiandrosterone. Aromatizing activity was examined in the presence and absence of cortisol and the rates of both oestrone and oestradiol synthesis were measured. Oestrone predominated in preference to oestradiol in most of the incubations, a result opposite to that found with human placentae. The sharp increase in the rate of oestradiol production found in the 144- to 146-day-old placentae incubated with testosterone may indicate a more rapid increase of aromatizing than of 17beta-hydroxysteriod dehydrogenase activity. The presence of cortisol in the mixtures did not significantly affect the placental aromatizing activity, indicating that there is no direct effect of cortisol on the enzyme system as measured in vitro. The dramatic rise of overall mean aromatizing activity from 4.86 plus or minus 0.22 (S.E.M.) at 138-141 days of gestation to 12.96 plus or minus 0.38 pmol/mg protein/min at 144-146 days (with a greater relative increase in the rate of oestradiol formation), suggests that changes in placental aromatizing activity may play an important role in maternal and foetal plasma oestrogen surges before ovine parturition.