Short-loop feedback control of luteinizing hormone in the rabbit

Molitch, Matthew; Edmonds, M.; Jones, EE; Wd, Odell

doi:10.1152/ajplegacy.1976.230.4.907

Cited by 31 publications

(20 citation statements)

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“…This svstem is remarkably sensitive and also specific (1,2 (6), and Ojeda and Ramirez (7) suggested the hypothalamus was the site for this control mechanism. However, considering the very complex circulatory systemn connecting hypothalamus and pituitary, alternative interpretations may be possible (8).…”

Section: Discussionmentioning

confidence: 99%

“…These animnals remained healthy and could be studied without anesthesia over several weeks' time. Unanesthetized animals were perfused for 240 min with sterile saline solution (0.19 ml/ min, 0.9% NaCl) as the control group, or hLH2 (2.75 IU/min) 1 Abbreviationts used int this paper: FSH, follicle-stimulating hormone; GnRH, gonadotropin-releasing hormone; hLH, human LH; LH, luteinizing hormone; rb-g, rabbit gamma globulin; rbLH, rabbit LH. 2 Highly purified hLH of immunochemical grade was kindly supplied by The Hormone Distribution Office, National Institutes of Arthritis and MIetabolic Diseases and perfused in 0.9% NaCI. through an indwelling catheter connected to a Harvard perfusion pump (Harvard Apparatus Co., Inc., Millis, Mass.).…”

Section: Ni Ethod Smentioning

confidence: 99%

“…Previous studies from this laboratory have directly demonstrated the existence of a short-loop feedback mechanism for control of luteinizing hormone (LH)l secretion in rabbits (1,2). These studies showed that as little as 1 IU of human LH (hLH) given as an intravenous bolus injection into ovariectomized rabbits decreased basal rabbit LH (rbLH) levels by more than 50% and indicated that this regulatory feedback is adequately sensitive to operate at physiological concentrations of LH.…”

Section: Introductionmentioning

confidence: 99%

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Pituitary Gland

Patritti-Laborde¹,

Wolfsen²,

Heber³

et al. 1979

J. Clin. Invest.

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A B S T R A C T The development of a species specific radioimmunoassay for rabbit luteinizing hormone (LH) has permitted the direct demonstration of LH feedback control of LH secretion (short-loop feedback control). In previous studies we showed that small bolus injections of human LH (hLH) intravenously administered to castrate female rabbits suppressed rabbit LH for 20-30 min. Human LH had no effect on rabbit follicle-stimulating hormone secretion. This control system was responsive to amounts of hLH estimated to be present in blood of eugonadal men and women. These studies were designed to determine whether this feedback control was exerted at a pituitary or hypothalamic level. Two groups of studies were carried out: (a) in vivo studies: Rabbit LH was quantified in the blood of castrated female New Zealand White rabbits receiving either constant hLH perfusion (2.75 IU/min) or saline perfusion, plus a bolus injection of 0.5, 6, or 20 ug of gonadotropin-releasing hormone (GnRH). Human LH decreased the response to 6 and 20 ,ug of GnRH by 31 and 36%, respectively, and abolished the response to 0.5 Ag, GnRH. (b) in vitro studies: Rabbit pituitary slices were incubated in the presence of medium alone, medium plus hLH (25 mIU/ml), medium plus GnRH (20 ,ag/ml), and medium plus both GnRH and hLH. hLH decreased basal rabbit LH release into the medium and abolished GnRH-stimulated rabbit LH release. hLH had no effect on rabbit follicle-stimulating hormone release. From these results we conclude that a direct and specific feedback control of LH on LH exists at a pituitary level.

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Section: Discussionmentioning

confidence: 99%

Section: Ni Ethod Smentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Pituitary Gland

Patritti-Laborde¹,

Wolfsen²,

Heber³

et al. 1979

J. Clin. Invest.

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“…We reported several characteristics of the inhibitory ultra-shortloop feedback mechanism controlling the gonado tropin secretion in rabbits [13,14,[17][18][19], Our previous studies showed its remarkable sensitivity, specificity, and for LH, identified the site for this control at the pituitary le vel. In the present studies, we evaluate possible participa tion of the a-and (3-subunits in this regulatory mechanism.…”

Section: Discussionmentioning

confidence: 99%

Effects of Alpha- and Beta-hCG Subunits on the Shortloop Feedback Control of Gonadotropins

Laborde¹,

Odell²

1981

Neuroendocrinology

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We have previously demonstrated that, in the rabbit, both LH and FSH secretions are controlled by shortloop feedback regulatory systems which are highly specific and sensitive. FSH secretion is suppressed by FSH; LH secretion is suppressed by LH and hCG. We have now evaluated the possible role of α- and β-subunits of hCG in the control of LH secretion in rabbits. Experiments were performed in unanesthetized castrated female rabbits bearing chronically implanted silastic catheters to permit repeated blood sampling without anesthesia. Intravenous injections of purified α- and β-chain of hCG were administered in dose levels from 10 to 300 μg, and blood samples were taken from -30 to 240 min before and after the bolus injections. Peripheral levels of rabbit FSH and LH were determined by RIA systems, which do not cross-react with intact hCG or its α- and β-subunits. By analysis of variance, no significant suppression of LH and FSH occurred in response to these doses of the subunits. Intact hCG, in doses of 1 μg, produced a sharp decrease in rabbit LH levels within 10 min. These in vivo studies demonstrate that there is no intrinsic activity of the dissociated purified α- and β-hCG sub-units on the shortloop feedback control of gonadotropins in the rabbit.

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“…Alternatively, extrahypothalamic area such as hippocampus may increase its inhibitory influence on responsiveness to the stimulation of the MPO (Kawakami et al, 1973) in the absence of ovarian steroids, and the inhibitory stimulus may counteract the facilitatory effect of the electrochemical stimulation of the MPO for LH-RH release. Furthermore, short-loop feedback action by the elevated serum LH on its secretion in OVX rats may influence on the MPO sensitivity to electrochemical stimulation (Molitch et al, 1976). Another possibility is that there is less readily releasable LH-RH store in the hypothalamus in OVX rats as indicated by lower hypothalamic content of LH-RH in OVX rats than that in intact rats (Araki et al, 1975).…”

Section: Discussionmentioning

confidence: 99%

Comparison of the effect of electrochemical stimulation of the medial preoptic area and the hypothalamic arcuate nucleus upon LH release in ovariectomized and proestrous rats.

Kawakami¹,

Higuchi²

1980

Endocrinol Japon

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The effect of electrochemical stimulation of the medial preoptic area (MPO) and the hypothalamic arcuate nucleus (ARC) on LH release was compared among longterm ovariectomized (OVX), ovariectomized rats treated with estradiol benzoate (OVX-F) and proestrous (PE) rats under pentobarbital anesthesia.The MPO stimulation failed to facilitate LH release in OVX rats whereas the stimulation increased serum LH levels in both OVX-E and PE rats. The ARC stimulation resulted in an elevation of serum LH in OVX and PE rats. The time course of serum LH elevation after the electrochemical stimulation of the MPO or the ARC was different between OVX-E and PE rats. In PE rats serum LH concentrations began to rise 20-30min after the stimulation of the MPO or the ARC with peak values obtained around70-90min.Serum LH started to elevate immediately with peak values in 10-20min following the ARC stimulation in OVX rats and the MPO stimulation in OVX-E rats. The time courses for changes in serum LH concentrations following LH-RH administration were similar in OVX and PE rats. From these results, the lack of circadian rhythm in serum LH levels in long-term OVX rats may be due to the inability of the MPO to re-spond to the stimulus generated from circadian pacemaker(s).The cause of the delay observed between the stimulation of the MPO and LH rise in PE rats may not exist in the levels of neural transmission between the MPO and the ARC or the pituitary, but in the level of the mediobasal hypothalamus.

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Short-loop feedback control of luteinizing hormone in the rabbit

Cited by 31 publications

References 0 publications

Pituitary Gland

Pituitary Gland

Effects of Alpha- and Beta-hCG Subunits on the Shortloop Feedback Control of Gonadotropins

Comparison of the effect of electrochemical stimulation of the medial preoptic area and the hypothalamic arcuate nucleus upon LH release in ovariectomized and proestrous rats.

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