Isolation of Luteinizing Hormone Receptor Binding Inhibitor from Ovine Corpora Lutea

Kumar, Narender; Kumari, G.L.; Dhir, Ravindra; Duraiswami, S.

doi:10.1080/07435808809032993

Cited by 3 publications

(4 citation statements)

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“…In testicular and ovarian extracts, low and high molecular weight FSH-binding inhibitors have been described (bovine testis (5-7); human and sheep ovaries (8); porcine follicular fluid (9,10)). Similarly, a factor which inhibits the binding of LH/hCG to its recep¬ tor has been reported in the testis (11,12) and the ovary (8,13,14). These gonadotropin-binding in¬ hibitors have also been observed in human serum (15,16) and in liver, kidney and thymus extracts (5,17).…”

mentioning

confidence: 66%

Evidence for LH-inhibiting activity in ovine peripheral and testicular blood

Papapdopoulos

Kamtchouing

Boujrad

et al. 1990

Acta Endocrinologica

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Intracellular cyclic AMP and testosterone productions by purified mature rat Leydig cells were stimulated by oLH (25 \g=m\g/l ) 18-and 12-fold, respectively, after a 5-h incubation period. The replacement of the incubation medium by charcoal-treated testicular venous plasma (40%, v/v) from adult rams in the breeding season induced an inhibition of cyclic AMP and testosterone productions (82 and 66%, respectively, of oLH-stimulated values). Testicular arterial plasma is less effective than testicular venous plasma, even when it originates from non-breeding season rams; in that case, testicular venous and arterial plasma strongly inhibit testosterone productions (84 and 67%, respectively of oLH-stimulated values), which probably indicates that the inhibitory activity is higher in the non-breeding season. The addition of peripheral plasma leads to a testosterone production equal to 35 and 65% of the oLH-stimulated values, respectively, for ram blood collected in non-breeding and breeding seasons. The same concentration of ovine testicular lymph or rete testis fluid is without significant effect on cyclic AMP production; however, testosterone is slightly decreased by lymph but enhanced by rete testis fluid. Increasing amounts of venous or arterial testicular blood induce a dose-related decrease of the specific binding of labelled hCG in both rat and ram testicular membranes. This inhibiting factor is present in peripheral and testicular blood of either control or hypophysectomized or castrated rams, is a protein in nature, heat-sensitive, and has an apparent molecular weight higher than 10 000 daltons. These results suggest the existence of a control of LH-specific binding to its receptors and of Leydig cell cyclic AMP and testosterone outputs; these activities are not species-specific and are more concentrated in testicular venous than in arterial blood. The origin of this inhibiting factor remains to be determined, since it is not confined to the testis and not of pituitary origin.The first step in the mechanism of gonadotropin action on Leydig cells is the interaction of the peptide hormone with specific receptors on the plasma membrane. After this binding, a series of events takes place, especially cyclicAMP formation, lead¬ ing to testosterone production. A local control of rat Leydig cell functions has been observed (1); indeed, both stimulatory and inhibiting factors produced by the seminiferous tubules modulate Leydig cell functions (2-4). Moreover, several re¬ ports deal with the existence of endogenous inhib¬ itors modulating the binding of gonadotropic hor¬ mones to their specific receptors. In testicular and ovarian extracts, low and high molecular weight FSH-binding inhibitors have been described (bovine testis (5-7); human and sheep ovaries (8); porcine follicular fluid (9,10)). Similarly, a factor which inhibits the binding of LH/hCG to its recep¬ tor has been reported in the testis (11,12) and the ovary (8,13,14). These gonadotropin-binding in¬ hibitors have also been observed in human serum (15,16) ...

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confidence: 66%

Evidence for LH-inhibiting activity in ovine peripheral and testicular blood

Papapdopoulos

Kamtchouing

Boujrad

et al. 1990

Acta Endocrinologica

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“…Active fraction of LHRBI (UM-2R-III) was prepared from sheep corpora lutea by an already published procedure (7).…”

Section: Methodsmentioning

confidence: 99%

“…Corrections were made for nucleotide interference. The peak protein fractions were checked for their LHRBI activity by radioreceptor assay following the procedure described earlier (7). This involved measuring inhibition of binding of 125 I-hCG to sheep luteal cells.…”

Section: Affinity Chromatography Of Um-2r-iiimentioning

confidence: 99%

“…Blood samples were collected at 9.00 h by femoral venipuncture from conscious monkeys on days 7,9,11,13,15,17,19, 23, 25, 27 and 29 during a control cycle in each monkey. These monkeys were then administered intravenous injections of UM-2R-III(A) in 200 mg/200 ml saline solution per dose in two doses at 9.30 h and again at 16.30 h on days 1 and 2 of the menstrual cycle.…”

Section: In Vivo Studies In Rhesus Monkeysmentioning

confidence: 99%

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Studies on LHRBI of Sheep Corpora Lutea—A Preliminary Report on In Vivo Administration to Rhesus Monkeys

Dhir

Kumari²

2004

Endocrine Research

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An LH-receptor binding inhibitor (LHRBI), previously isolated from sheep corpora lutea in a partially purified form was subjected to wheat germ lectin chromatography. The unadsorbed fraction (UM-2R-III A) thus obtained had maximum LHRBI activity. This preparation was utilized to develop polyclonal antibodies. The purified fraction could be radioiodinated, suggesting its peptide nature. Intravenous injections of UM-2R-IIIA at 200 microg protein per dose in two doses per day at 9.30 h and 16.30 h on days 1 and 2 of the menstrual cycle to regularly cycling monkeys resulted in a shortening of the length of the cycle by 2 to 3 days. In addition, serum levels of progesterone increased prior to ovulation and remained high through the cycle of all three treated monkeys. It is possible that LHRBI induced enhanced synthesis and/or secretion of progesterone by the ovarian follicles thus suggesting a role for LHRBI in ovarian function.

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