Bernard F. Rice

The gonadotropin receptor of the human corpus luteum

Abstract Homogenates of human corpora lutea specifically bound 125 I-human luteinizing hormone (HLH). This binding was proportional to tissue (receptor) concentration and the receptor was saturable. Binding of 125 I-HLH was markedly reduced at 4° C. or in the presence of 10 I.U. human chorionic gonadotropin (HCG) or 2.4 I.U. of HLH (LER-907). LH from other species (ovine, bovine, and porcine) as well as other trophic hormones tested did not compete with 125 I-HLH. Specific binding of 125 I-ovine or 125 I-bovine LH could not be demonstrated. An apparent dissociation constant (Kd) of ∼3 and ∼9 × 10 −9 M was observed for two corpora lutea (Day 28 and Day 16) with lactoperoxidase labeled 125 I-HLH. In examining 125 I-HLH binding from over thirty corpora lutea from different times of the menstrual cycle, it was concluded that midluteal phase corpora lutea bound more 125 I-HLH than did older or younger corpora lutea. Day 14 corpora lutea and aged corpora lutea did not specifically bind 125 I-HLH. Ovarian stromal tissue failed to specifically bind 125 I-HLH, even when derived from ovaries that yielded corpora lutea which did bind 125 I-HLH. These results indicate that the human corpus luteum possesses a specific LH receptor. This receptor appears to require a conformation thus far found only in HLH and HCG.

Luteoma of pregnancy: Steroidogenic and morphologic considerations

Abstract Steroid hormone content and steroid synthesis in vitro were studied in a clinically and morphologically typical luteoma of pregnancy. The only Δ 4 -3-ketosteroid present was tentatively identified by paper and thin-layer chromatography as Δ 4 -androstene-3,17-dione. Net synthesis (μg) of this androgen was augmented in vitro by HCG. No radioactive steroid formation from acetate-1- 14 C could be established after analysis by reverse isotope dilution. The biochemical and histologic data suggest that the luteoma of pregnancy originates from the ovarian stroma. The augmentation of steroidogenesis by HCG in vitro in this study and the clinical observation of postpartum regression in other studies are compatible with the concept that the placental gonadotropin plays some role in development and maintenance of this specific ovarian lesion.

Steroid hormone formation in the human ovary: III. Action of gonadotropins on testosterone synthesis by normal ovarian stromal tissue

Abstract The biosynthesis of radioactive testosterone in vitro from acetate-1-14C by normal human ovarian stromal tissue is described. Testosterone formation appears to be augmented in vitro by human chorionic gonadotropin and 2 human pituitary preparations containing luteinizing hormone activity.

Dehydrogenation of Reduced Pyridine Nucleotides by Leydig Cell Tumors of the Rat Testis

Summary The activities of the cytochrome c reductases and of the D-T diaphorase in rat Leydig cell tumors have been described. The increase in enzymatic activity of the NADH cytochrome c reductase activity in functional tumors derived from interstitial cells of the rat testis is interpreted as being possibly related to hydroxylation of steroids by the neoplastic cells. Meanwhile, the increase in the activity of the D-T diaphorase in the other tumor is interpreted as being an anaplerotic reaction to substitute for the deficient shuttles for the transfer of reducing equivalents from the cytoplasm to the mitochondria observed in tumors.

Evaluation of epitestosterone and testosterone excretion in polycystic ovary disease and other ovarian disorders.

Abstract Urine excretion of epitestosterone and testosterone has been measured in patients with functional ovarian abnormalities. These included patients with known polycystic ovary syndrome treated by wedge resection, suspected polycystic ovary syndrome treated medically, patients with primary ovarian failure, and pregnancy with hirsutism. Patients with polycystic ovary syndrome had a characteristic increase in excretion of epitestosterone following ovarian stimulation with human chorionic gonadotropin. Measurement of testosterone was less helpful in predicting the presence of polycystic ovaries. Measurement of epitestosterone was also found to be of value in detecting primary ovarian failure where epitestosterone levels are very low and response to HCG stimulation is minimal. The measurement of urine epitestosterone before and after stimulation with HCG appears to be a useful confirmatory test of ovarian stromal hyperfunction in the anovulatory patient suspected of having polycystic ovarian disease.

A method for determination of the specific activity of receptor-bound human chorionic gonadotropin (hCG).

Precise knowledge of the specific activity (S.A., muc/mug) of the receptor bound radiolabelled hormone is required for study of the stoichiometry of peptide hormone-receptor interactios. A radioligand receptor assay using 131-I-hCG as tracer and transplantable mouse luteoma homogenates (Biol. Reprod. 8:550, 1973) as a source of receptor was used as a model to determine the specific activity of receptor bound 125-I-hCG. Progressive saturation of the gonadotropin receptor by 125-I-hCG suggests the presence of a high affinity-low capacity binding event (saturating between 14 and 37 ng/100 mg homogenate) that does not distinguish between non-radioactive hCG and 125-I-hCG, and a low affinity-high capacity binding event (saturating between 240 and 270 ng/100 mg homogenate) that shows a preference for non-radioactive hCG over 125-I-hCG. Parallelism between bound 125-I-hCG and non-radioactive hCG in terms of competition with tracer 131-I-hCG could only be demonstrated for the high affinity event.

The Specificity of Gonadotropin Binding by the Human Corpus Luteum*†*Supported in part by Grant FR-05518 from the National Institutes of Health, a grant from the Greater New Orleans Cancer Association, and the Starr Research Fund.†Presented in part at the Thirtieth Annual Meeting of The American Fertility Society, April 4 to 6, 1974, Hollywood, Fla.

The specificity of gonadotropin binding was studied in fresh and frozen human corpora lutea. Ovine, bovine, and porcine luteinizing hormone (LH) competed with 125I-labeled human LH (125I-hLH) and 125I-labeled human chorionic gonadotropin (125I-hCG) for binding to tissue receptors in homogenates of human corpora lutea frozen for 3 to 12 months. In contrast, oLH, bLH, and pLH competed minimally for 125I-hLH and 125I-hCG binding sites in homogenates of fresh human corpora lutea. Ovine follicle-stimulating hormone (FSH) and thyroid-stimulating hormone (TSH) did not compete in homogenates of fresh or frozen tissue. Competition of oLH and hCG for 125I-hCG binding sites at several dose levels in a homogenate of a fresh corpus luteum was studied. One hundred micrograms of oLH and ten nanograms of hCG gave an equivalent competition--a 10,000-fold difference in competitive potency. Only hCG competed with 125I-hCG for binding when the competition of oLH, bLH, pLH, oFSH, oTSH, hCG and hCG subunits, and hCG were compared at the 10-mug level in a homogenate of fresh human corpus luteum. The binding of 125I-labeled homologous human hormones by the corpus luteum was examined in a limited fashion. 125I-Prolactin did not bind to preparations of fresh stroma from a patient with polycystic ovaries nor did it bind to three separate preparations of fresh corpora luteum which did bind 125I-hCG. 125I-hTSH did not show significant binding to a fresh human corpus luteum preparation which did bind 125I-hCG. These studies indicate that the gonadotropin receptor of the fresh human corpus luteum possesses a unique species specificity and illustrate the importance of working with human corpora lutea in their most native state.