Luteal Luteinizing Hormone Receptors Research Articles

In vivo intra-luteal implants of prostaglandin (PG) E 1 or E 2 (PGE 1, PGE 2) prevent luteolysis in cows. II: mRNA for PGF 2α, EP1, EP2, EP3 (A–D), EP3A, EP3B, EP3C, EP3D, and EP4 prostanoid receptors in luteal tissue

Previously, it was reported that chronic intra-uterine infusion of PGE 1 or PGE 2 every 4 h inhibited luteolysis in ewes by altering luteal mRNA for luteinizing hormone (LH) receptors and unoccupied and occupied luteal LH receptors. However, estradiol-17β or PGE 2 given intra-uterine every 8 h did not inhibit luteolysis in cows, but infusion of estradiol + PGE 2 inhibited luteolysis. In contrast, intra-luteal implants containing PGE 1 or PGE 2 in Angus or Brahman cows also inhibited the decline in circulating progesterone, mRNA for LH receptors, and loss of unoccupied and occupied receptors for LH to prevent luteolysis. The objective of this experiment was to determine how intra-luteal implants of PGE 1 or PGE 2 alter mRNA for prostanoid receptors and how this could influence luteolysis in Brahman or Angus cows. On day-13 Angus cows received no intra-luteal implant and corpora lutea were retrieved or Angus and Brahman cows received intra-luteal silastic implants containing Vehicle, PGE 1, or PGE 2 and corpora lutea were retrieved on day-19. Corpora lutea slices were analyzed for mRNA for prostanoid receptors (FP, EP1, EP2, EP3 (A–D), EP3A, EP3B, EP3C, EP3D, and EP4) by RT-PCR. Day-13 Angus cow luteal tissue served as pre-luteolytic controls. mRNA for FP receptors decreased in day-19 Vehicle controls compared to day-13 Vehicle controls regardless of breed. PGE 1 and PGE 2 up-regulated FP gene expression on day-19 compared to day-19 Vehicle controls regardless of breed. EP1 mRNA was not altered by any treatment. PGE 1 and PGE 2 down-regulated EP2 and EP4 mRNA compared to day-19 Vehicle controls regardless of breed. PGE 1 or PGE 2 up-regulated mRNA EP3B receptor subtype compared to day-19 Vehicle control cows regardless of breed. The similarities in relative gene expression profiles induced by PGE 1 and PGE 2 support their agonistic effects. We conclude that both PGE 1 and PGE 2 may prevent luteolysis by altering expression of mRNA for prostanoid receptors, which is correlated with changes in luteal mRNA for LH receptors reported previously in these same cows to prevent luteolysis.

In vivo intra-luteal implants of prostaglandin (PG) E 1 or E 2 (PGE 1, PGE 2) prevent luteolysis in cows. I. Luteal weight, circulating progesterone, mRNA for luteal luteinizing hormone (LH) receptor, and occupied and unoccupied luteal receptors for LH

Previously, it was reported that chronic intra-uterine infusion of PGE 1 or PGE 2 every four hours inhibited luteolysis in ewes. However, estradiol-17β or PGE 2 given intra-uterine every 8 h did not inhibit luteolysis in heifers, but infusion of estradiol + PGE 2 inhibited luteolysis in heifers. The objective of this experiment was to determine whether and how intra-luteal implants containing PGE 1 or PGE 2 prevent luteolysis in Angus or Brahman cows. On day-13 post-estrus, Angus cows received no intra-luteal implant and corpora lutea were retrieved or Angus and Brahman cows received intra-luteal silastic implants containing Vehicle, PGE 1, or PGE 2 and corpora lutea were retrieved on day-19. Coccygeal blood was collected daily for analysis for progesterone. Breed did not influence the effect of PGE 1 or PGE 2 on luteal mRNA for LH receptors or unoccupied or occupied luteal LH receptors did not differ ( P > 0.05) so the data were pooled. Luteal weights of Vehicle-treated Angus or Brahman cows from days-13–19 were lower ( P < 0.05) than those treated with intra-luteal implants containing PGE 1 or PGE 2. Day-13 Angus luteal weights were heavier ( P < 0.05) than Vehicle-treated Angus cows on day-19 and luteal weights of day-13 corpora lutea were similar ( P > 0.05) to Angus cows on day-19 treated with intra-luteal implants containing PGE 1 or PGE 2. Profiles of circulating progesterone in Angus or Brahman cows treated with intra-luteal implants containing PGE 1 or PGE 2 differed ( P < 0.05) from controls, but profiles of progesterone did not differ ( P > 0.05) between breeds or between cows treated with intra-luteal implants containing PGE 1 or PGE 2. Intra-luteal implants containing PGE 1 or PGE 2 prevented ( P < 0.05) loss of luteal mRNA for LH receptors and unoccupied or occupied receptors for LH compared to controls. It is concluded that PGE 1 or PGE 2 alone delays luteolysis regardless of breed. We also conclude that either PGE 1 or PGE 2 prevented luteolysis in cows by up-regulating expression of mRNA for LH receptors and by preventing loss of unoccupied and occupied LH receptors in luteal tissue.

Corpora lutea induced by gonadotrophin-releasing hormone treatment of anoestrous Welsh Mountain ewes: reduced sensitivity to luteinizing hormone in vivo and to chorionic gonadotrophin in vitro

Seasonally anoestrous Welsh Mountain ewes received 250 ng gonadotrophin-releasing hormone (GnRH) every 2 h, with (Group 1; n=13) or without (Group 2; n=14) progesterone priming for 48 h. Fourteen control ewes (Group 3) were studied during the luteal phase in the breeding season. Animals in Group 4 (n=12) received progesterone priming followed by 250 ng GnRH at increasing frequency for 72 h, while ewes in Group 5 (n=13) were given three bolus injections of 30 microg GnRH at 90-min intervals. All treatment regimens induced ovulation. However, only corpora lutea (CL) from ewes in Group 3 (breeding season) or Group 4 exhibited normal luteal function. Luteal luteinizing hormone (LH) receptor levels were significantly higher on day 12 than day 4, and CL from groups with adequate CL (3 and 4) had significantly higher (125)I-human chorionic gonadotrophin (hCG)-binding levels than the three groups with inadequate CL on day 12. LH-binding affinity was unchanged. Exogenous ovine LH (10 microg) in vivo on days 3 or 11 after ovulation induced a pulse of progesterone in ewes with adequate CL: however, ewes in Groups 1, 2 and 5 showed no significant response. Basal progesterone secretion in vitro was significantly greater on day 4 than on day 12. Maximal steroidogenic responses of adequate and inadequate CL to hCG and to dibutyryl cyclic-3',5'-AMP were similar at both stages of the luteal phase. However, the EC50 for hCG on days 4 and 12 was 10-fold lower for groups with an adequate CL (0.1 IU hCG/ml) than for inadequate-CL groups (1 IU hCG/ml; P <0.05). Thus, in addition to the well-characterized premature sensitivity of GnRH-induced inadequate CL to endometrial luteolysin, we have shown (1) a marked decrease in total number of cells in the CL, a profound reduction in vascular surface area, and a decrease in mean large luteal cell volume (with no change in large luteal cell numbers), (2) decreased luteal LH receptor and progesterone content compared with adequate CL and (3) that CL that were becoming, or were destined to become, inadequate failed to respond to ovine LH in vivo and were 10-fold less sensitive to hCG in terms of luteal progesterone secretion in vitro.

Relationship of circulating steroid hormones, luteal luteinizing hormone receptor and progesterone concentration, and embryonic mortality during early embryogenesis in the domestic cat.

Serum hormones, corpus luteum (CL) progesterone, and CL LH receptors were characterized and interrelated to ovarian follicle and CL number and preimplantation embryo quality/survival in the cat. Blood samples were collected from queens ovariohysterectomized at 64 (n = 7), 76 (n = 11), 100 (n = 8), 124 (n = 7), 148 (n = 6), or 480 (n = 8) h after first copulation (3-times-daily matings on Days 2 and 3 of estrus). Ovarian CL were enucleated, weighed, and bisected; one hemi-CL was assayed for progesterone and the other for LH receptors. Serum was assessed for estradiol-17 beta and progesterone. Serum estradiol-17 beta concentrations did not return (p > 0.05) to baseline approximately 20 pg/ml) until 124 h after first copulation, whereas serum progesterone began to increase (> 1 ng/ml) by 76 h, was elevated (p < 0.05) by 124 h, and continued to rise thereafter. Serum progesterone was highly correlated with CL mass and LH receptor and progesterone concentration (range, r = 0.69-0.82; p < 0.01). CL progesterone and LH receptor concentrations were similar (p > 0.05) at 64 and 76 h, and both increased (p < 0.05) at subsequent time intervals and were correlated closely (r = 0.65; p < 0.01). Although ovarian CL were distinct and well organized by 64 h, pronounced elevations in serum progesterone and CL LH receptors and progesterone did not occur until at least 36 h later. The rapid increase in serum progesterone concentrations between 100 and 148 h was related to accelerated LH receptor synthesis and CL progesterone production and not entirely to enhanced CL growth.(ABSTRACT TRUNCATED AT 250 WORDS)

Corpus luteal insufficiency

The corpus luteum is controlled by luteinizing hormone (LH) and intraovarian morphofunctional specialization and autocrine/paracrine mechanisms. Corpus luteal insufficiency produces luteal phase defects (LPD). The poor precision and validation of endometrial histologic dating and single or random multiple serum progesterone measurements produce widely variable diagnoses. The true prevalence rate of LPD may be only 3-5% similar to that due to chance. The role of LPD in causing infertility can be challenged because the diagnosis is not predictive of recurrence in subsequent cycles, and other causes of infertility are not controlled for. Intraobserver and interobserver variability, uterine site of biopsy, luteal phase length, time of ovulation, and luteal phase timing of biopsy have been examined and have confirmed the imprecision of dating as a sensitive and reliable assessment of luteal insufficiency. There is support for either early or late luteal phase biopsy. Endometrial dating using LH timing as a reference point is relatively more reliable. Integrated luteal progesterone is the only currently accurate assessment of luteal sufficiency. Clomiphene does not increase LPD but increases serum progesterone, integrated progesterone, corpus luteum LH/human chorionic gonadotropin (hCG), and insulin-like growth factor-1 (IGF-1) receptors, all of which promote increased progesterone production and do not affect endometrial estrogen and progesterone receptors. hCG is more likely to stimulate progesterone production if given at the mid rather than early luteal phase corresponding to the phase with highest total and available (unoccupied) corpus luteal LH receptors. Careful analysis of published studies on treatment of LPD revealed only one randomized controlled study, and, statistically, all studies revealed no better outcome with progesterone treatment.

LUTEOLYTIC ACTION OF PROSTAGLANDINS IN SWINE AND THE EFFECTS OF CLOPROSTENOL ON LUTEINIZING HORMONE RECEPTORS AND MEMBRANE STRUCTURE OF PORCINE CORPORA LUTEA

The luteolytic action of prostaglandin F2α (PGF2α), 15-keto-PGF2α, 15-methyl-PGF2α, and cloprostenol was evaluated in cycling gilts and sows after intramuscular injection on day 13 of the estrous cycle. Only cloprostenol significantly shortened the mean cycle length (18.5 vs. 20.3 d, P &lt; 0.05). Cloprostenol also caused a more rapid decline in serum progesterone concentrations than did the other prostaglandins. Serum concentrations of the prostaglandin metabolite 13,14-dihydro-15-keto-PGF2α (PGFM), showed rapid transitory peaks after PGF2α or 15-keto-PGF2α and a lower, later rise after cloprostenol. A second experiment examined luteal luteinizing hormone (LH) receptors and luteal membrane ultrastructure during the estrous cycle and pregnancy and the effect of cloprostenol on these parameters during the estrous cycle. The number of unoccupied luteal LH receptors, as measured by specific 125I-hCG binding, dropped significantly from mid to late pregnancy and from mid to late cycle. Cloprostenol lowered serum progesterone concentrations but did not affect hCG binding. X-ray diffraction showed no correlation of gel or liquid-crystalline phase lipids in luteal microsomes with the stage of the estrous cycle or pregnancy or cloprostenol treatment. Key words: Swine, luteolysis, estrous cycle, prostaglandins, luteal LH receptors

First postpartum ovulations and corpora lutea in ewes which lamb in the breeding season

Two experiments involving crossbred ewes which lambed during the breeding season were performed to determine whether: (a) the interval to first postpartum ovulation could be reduced by weaning or mastectomy; (b) there are differences in luteal structure and luteinizing hormone (LH) receptor concentration between first postpartum corpora lutea induced with GnRH and normal cycling corpora lutea and (c) pretreatment of postpartum ewes with progesterone would affect luteal LH receptor concentration and luteal phase serum progesterone concentration. In experiment I, the mean interval (±SEM) to the first postpartum ovulation was 22.3 ± 1.1 days and was not significantly altered by weaning or mastectomy. More than half of the ewes had small, short-lived peaks of serum progesterone associated with short-lived corpora lutea prior to the normal luteal phase rise of serum progesterone. In experiment II, 2 h after GnRH injection on day 18 postpartum, serum LH concentrations were higher in ewes which received progesterone treatment on days 13 and 14 than in control ewes. Progesterone treatment did not affect mean corpus luteum weight (157 mg) or concentration of LH receptors (0.95 fmol/mg) in first postpartum corpora lutea, but progesterone-treated ewes had significantly higher endogenous serum progesterone concentrations on days 21–24. GnRH-induced corpora lutea from postpartum ewes were lighter in weight, paler in color, had lower LH receptor concentrations and had a more regressed histological appearance than corpora lutea of a similar age from normal, cycling ewes.

Luteal luteinizing hormone receptors during the postovulatory period in the mare.

Changes in serum luteinizing hormone (LH) and progesterone concentrations, number of luteal unoccupied LH receptors, receptor affinity constants, luteal weights and luteal progesterone concentrations were determined during the postovulatory period in the mare. The number of unoccupied LH receptors and receptor affinity was less during the early (Days 1-4) and late [Day 15 through 3rd day after start of corpus luteum (CL) regression] luteal phases than during the mid-luteal (Days 9-14) phase of the postovulatory period (P less than 0.01). The number of LH receptors per CL increased 21-fold (P less than 0.001) from Day 1 to Day 14. Receptor affinity increased 5-fold (P less than 0.001) from Day 1 to Day 13. Receptor number was highly correlated with receptor affinity (P less than 0.01) and both were highly correlated with serum and luteal progesterone (P less than 0.01). During regression of the CL, the number of LH receptors and receptor affinity decreased concomitantly with serum and luteal progesterone. Morphologically, luteal cell development and degeneration correlated with the change in receptor numbers, affinity constants and luteal and serum progesterone concentrations. Receptor number and affinity, luteal weight and serum and luteal progesterone concentrations did not differ between the CL from multiple ovulations. Random variations in the data observed between CL from multiple and single ovulations suggested that CL from the two groups were not different in structure and function. In summary, the above results suggest that major factors in regulation of progesterone secretion and maintenance of the equine CL are changes in the number of LH receptors and the affinity constants throughout the postovulatory period.

Obligatory role of luteinizing hormone (LH) in the initiation of preovulatory follicular growth in the pregnant rat: specific effects of human chorionic gonadotropin and follicle-stimulating of hormone on LH receptors and steroidogenesis in theca, granulosa, and luteal cells.

The changes in serum hormone concentrations accompanying preovulatory follicular development at the end of pregnancy in the rat suggest that follicular maturation is stimulated by subtle increases in serum LH and/or by a decrease in serum progesterone but not by increases in serum FSH. To test the ability of small antral nonovulatory follicles to respond to subtle increases in LH-like activity in the presence of elevated serum progesterone, hCG (0.25 to 3.0 IU), or the control, human FSH (hFSH) (0.88 to 4.4 IU) was administered twice daily to rats on days 14 and 15 of pregnancy. hCG stimulated follicular growth, increased granulosa cell and theca cell LH receptor content, and enhanced follicular estradiol accumulation in a time-related and dose-dependent manner. Follicles from animals treated twice daily for 2 days with 1.5 IU hCG (3.5 pmol) were by day 16 functionally identical to proestrous follicles isolated on day 23, and a bolus injection of 10 IU hCG was able to induce ovulation in these hCG-primed animals. Although 35.5 pmol hFSH caused granulosa cell LH receptor content and aromatase activity to increase, hCG was clearly much more effective on a “per mole” basis in evoking these responses. FSH failed to increase either theca cell LH receptor content or the inherent ability of follicles to produce estradiol when wholly dependent on endogenous androgen substrate. In addition, 2 days of treatment with hCG caused dose-dependent decreases in LH receptor content of luteal tissue but did not alter serum concentrations of progesterone, suggesting that luteal cell progesterone production may not be associated with the luteal LH receptor response system at this time. Results of this study suggest that, even in the presence of elevated serum progesterone, sustained increases in serum LH (but not FSH) activity will support the maturation of preovulatory follicles that are functionally indistinguishable from proestrous follicles. The dependence of follicular differentiation on LH appears to involve enhancement of theca cell function and synthesis of aromatizable androgens rather than stimulation of granulosa cell aromatase activity.

Antiserum against rat luteinizing hormone (LH) receptors

Summary An antiserum to soluble rat luteal LH receptors was produced in rabbits. The presence of LH receptor antibodies was shown by indirect immuno-precipitation of [125]hCG-soluble rat LH receptor-receptor antiserum complexes by antirabbit IgG. The antiserum bound LH receptors from rat ovaries and testes but not those from human or sheep ovaries. Unoccupied LH receptors competed with [125I]hCG occupied receptors in a dose-dependent fashion for antiserum binding. Extracts of rat brain and liver did not appear to bind to the antiserum. In addition, LH-dependent progesterone secretion from isolated rat ovarian cells was reduced by the antiserum although there was no change in hormone binding.

Luteal Cell Receptor Content for Prolactin (PRL) and Luteinizing Hormone (LH): Regulation by LH and PRL1

The effect of LH and PRL during the differentiation of granulosa cells to luteal cells was examined by determining the ability of LH and PRL to regulate luteal cell receptor content for these hormones and to increase production of progesterone. Preovulatory follicles and corpora lutea were hormonally induced in immature hypophysectomized female rats by sequential treatment with estradiol, hFSH and oLH. The content of receptor for LH was high in granulosa cells of large antral follicles. Administration of LH caused receptor for LH to decrease markedly within 24 h and to remain low for 96 h. In contrast, granulosa cell content of receptor for PRL increased progressively for 48 h following LH stimulation and remained elevated in fully luteinized cells at 96 h. This increase in PRL receptor appears to be functionally related to the ability of luteal cells to respond to PRL. When PRL was given for 4 days after LH, both luteal cell progesterone production and LH receptor content increased progressively after, but not before, 48 h. Since these changes occurred in the absence of LH, the increase in LH receptor appears to be a consequence of, but not a requirement for, the PRL-induced increase in progesterone production. If daily injections of PRL were delayed for 72 or 96 h following LH induction of lutenization, luteolytic rather than luteotropic effects of PRL were observed. Since receptor for PRL remained elevated at 72 and 96 h, intracellular mechanisms and not receptor content, appear to be effecting the response of luteal cell to PRL.