Dose Of LHRH Research Articles

Induction of LH surges by continuous infusion of LH-RH1.

Preovulatory LH surges were measured in cannulated proestrous rats. Such LH peaks were also obtained by infusing pentobarbital-blocked animals with LH-RH for periods of up to 20 h; this suggested that the pituitary LH stores were exhausted. However, the total amount of LH secreted appeared more or less determined by the LH-RH dose, indicating that the size of the releasable LH pool is not fixed.

Effect of luteinizing hormone releasing hormone (LHRH) and an LHRH antagonist of hypothalamic and plasma LHRH of hypophysectomized rats.

Stalk-medium eminence (SME) and plasma LHRH activities of chronically hypophysectomized immature female rats were evaluated by bioassay following a single subcutaneous injection of varying doses of either LHRH or the LHRH antagonist, [D-Phe2, D-Ala6]-LHRH (Wy-18,185). Administration of LHRH to hypophysectomized rats produced parallel dose-related increases in SME and plasma LHRH activities. Wy-18,185 produced a similar, but attenuated dose-related increase in SME-LHRH activity, while a dose-related decrease in plasma LHRH activity was observed. Collectively, the data suggest that (1) exogenous LHRH may be sequestered by the hypothalamus leading to significant increases in hypothalamic LHRH content, and (2) peptide antagonists of LHRH inhibit the release of endogenous LHRH at the hypothalamic level.

Clinical investigations for emotional effects of neuropeptide hormones

After the demonstration that hypothalamic peptides can have a direct effect on the central nervous system, a series of studies was initiated to investigate the hypothesis that hypothalamic peptides could have an effect on emotions and affect. TRH was administered to 6 patients with endogenous depressions in a double-blind, cross-over design with transient improvement in the mental depression of 4 of the 6 patients. In a second study involving 8 seriously depressed patients given 1000 μg of TRH for 10 days, no significant antidepressant effect of TRH was observed. In a pilot, double-blind study of 18 women with endogenous depressions, the group receiving MIF-1 60 mg per day in a single daily dose for 6 days responded better than the placebo group, which in turn responded better than the group receiving MIF-1 150 mg per day. In a second, double-blind study testing MIF-1 in endogenous depressions, 5 patients met the criteria for subtstantial improvement out of a total of 8 receiving MIF-1 75 mg per day. In contrast, only one patient met these criteria in each of the remaining 2 groups, consisting of 10 patients receiving MIF-1 750 mg per day and 5 patients receiving placebo. Finally, 6 men complaining of decreased libido and/or potency were given intravenous injections of LHRH 700 μg or saline once daily for 3 consecutive days per week in a double-blind, cross-over design. In addition, 3 men were given much higher doses of LHRH in a single-blinded study. No substantial effect on libido or sexual performance was observed.

Effects of progesterone and synthetic luteinizing hormone releasing hormone on the release of luteinizing hormone during sexual maturation in the hen (Gallus domesticus).

Single intramuscular injections of 0-5 mg progesterone/kg resulted in increased LH secretion in laying hens but not in pullets with completely undeveloped sexual organs. Injections of the steroid were first able to stimulate LH release 8-10 weeks before the onset of lay when the comb, ovary and oviduct had started to grow and basal plasma LH concentrations were beginning to rise. At this time, injecitons of 10 mug synthetic LH-RH/kg resulted in an incremental change in plasma LH levels of around 26 ng/ml. A similar incremental change was observed after giving the same dose of LH-RH to pullets with no signs of sexual development. Three to four weeks before the first eggs were laid, basal plasma LH levles started to fall, the pituitary became progressively more insensitive to synthetic LH-RH and injections of 0-5 mg progesterone/kg resulted in a reduced LH response. Ten mug LH-RH/kg caused incremental changes in blood levels of LH of less than 5 ng/ml. The final stage of sexual maturation occurred during the week before the onset of lay and was characterized by a rapid growth of large yolky ovarian follicles and a further fall in the sensitivity of the pituitary to synthetic LH-RH. However, injections of 0-5 mg progesterone/kg resulted in a prolonged release of LH. These observations are discussed in relation to the maturatio of the positive feedback mechanism by which progesterone stimulates the secretion of LH.

An evaluation of the diagnostic value of synthetic luteinizing hormone releasing hormone.

The potential use of LH-RH as a test of pituitary function in women has been investigated. In this study the synthetic material was administered intravenously, and samples of peripheral blood were removed at defined times. The levels of plasma oestradiol, LH and FSH were determined by radioimmunoassay. The administration of incremental doses of LH-RH (from 1.56 to 450 mug) demonstrated that a maximal response was obtained with 100 mug in the majority of apparently healthy subjects. Accordingly, this amount was selected as the standard dose for use in a test of pituitary function. The application of this test to 96 patients with secondary amenorrhea showed that the release of LH and FSH (as assessed by the maximum value, and the area under the response curve) was within the normal range in 82, high in 4 and low in 10. There was no correlation between the cause of the amenorrhea, the results of the LH-RH test, and the endogenous levels of oestradiol, LH and FSH. In addition 5 patients with primary amenorrhea and 8 patients with pituitary disorders were tested with LH-RH. In primary amenorrhea low basal levels of LH were found, but all subjects had a normal response to LH-RH. In 3 patients with clinical hypopituitarism the basal levels of gonadotrophins were in the normal range, but there was an impaired response to LH-RH. It is concluded that 100 mug of LH-RH administered intravenously may be used to test the ability of the pituitary to release LH and FSH, but the magnitude and duration of the response is not of additional diagnostic value.

Effect of prolonged LH-releasing hormone administration on gonadotropin response in patients with hypothalamic and pituitary tumors.

The effect of prolonged administration of synthetic LH-RH (400 mug daily im for 5 days) on gonadotropin response to LH-RH (100 mug single injection iv) was compared in 13 patients with pituitary tumors or suprasellar tumors. No patients with pituitary tumors exhibited an augmented response on serum FSH and LH after prolonged LH-RH administration. A paradoxical fall in response to LH-RH test occurred in 3 patients with pituitary tumors and in a patient with hypothalamic tumor in whom gonadotropin responses were normal on the first LH-RH test. On the other hand, 2 patients with suprasellar tumors with a low response to the initial LH-RH test showed significant increase on a second LH-RHtest after consecutive LH-RH administration. Consecutive administration of LH-RH may help to distinguish between the hypogonadism of pituitary origin and that of hypothalamic origin when the initial LH response to a single dose of LH-RH is subnormal.

Increased and prolonged LH-RH/FSH-RH activity of synthetic (D-Ala6, Des-Gly-NH210)-LH-RH-ethylamide in normal women

A synthetic LH-RH analogue (D-Ala6, Des-Gly-NH210)-LH-RH ethylamide exhibited an increased and prolonged LH-RH/FSH-RH activity in normal women. The integrated amounts of LH and FSH levels for this LH-RH analogue were about nine and five times greater than for the same doses of synthetic LH-RH. It is expected that this synthetic LH-RH analogue might yield more positive results than with LH-RH when used in infertility problems.

In vitro pituitary responsiveness to gonadotropin-releasing hormone (LH-RH) in intact and castrated male and female rats

The in vitro response of pituitaries isolated from both normal and 18–21-day post-castration male and female intact rats to incremental doses of synthetic gonadotropin-releasing hormone (LH-RH) has been investigated. Intact male pituitaries released luteinizing hormone (LH) maximally at the smallest dose of LH-RH (0.1 ng/ml) whereas intact female pituitaries released LH in a dose-response fashion. FSH release from intact male pituitaries was considerably greater than that from intact female pituitaries. As with LH, intact male pituitaries appeared maximally stimulated at 0.1 ng/ml of LH-RH. Intact female pituitaries did not release FSH until a 10 ng/ml dose of LH-RH was used. Male and female castrate pituitaries were more susceptible to LH-RH-induced LH and FSH release than were their intact counterparts, although this was more pronounced with regard to LH release. In addition castrate male pituitaries were more sensitive to lower doses of LH-RH than were castrate female pituitaries, this being most pronounced regarding LH release. Castrate female pituitaries released less FSH at the 100 ng/ml dose than at the 10 ng/ml dose, possibly indicating inhibition at these higher doses. In addition, pituitary extraction and serum from normal and castrate male and female rats were examined for LH and FSH content. LH content of castrated rat pituitaries of both sexes was considerably greater than that of their intact counterparts, as expected. However, castrate male pituitaries contained significantly less FSH than intact male pituitaries, whereas the opposite was true for the female groups. Serum LH and FSH levels were increased in the castrate groups with no difference between sexes. Serum from intact males contained considerably more FSH than did the serum from intact females.

ChemInform Abstract: SYNTHESIS AND BIOLOGICAL ACTIVITY OF LH‐RH ANALOGS MODIFIED AT THE CARBOXYL TERMINUS

Des(Pro9,Gly10)-LH-RH ethylamide, des(Pro9,Gly10)-LH-RH butylamide, desGly10-LH-RH 2-aminoethylamide, and desGly10-LH-RH hydrazide were synthesized by a solid-phase method involving cleavage of protected peptide intermediates from their resin support by reaction with ethylamine, butylamine, ethylenediamine, and hydrazine, respectively. In the assay utilizing steroid pretreated, ovariectomized rats, the peptides were found to have the following LH-releasing activities when compared with natural LH-RH: ethylamide, 0.2%; butylamide, 0,1%; 2-aminoethylamide, 2.4%; hydrazide, 12%. DesGly10-LH-RH hydrazide was used as a precursor in the synthesis of desGly10-LH-RH allylamide and desGly10-LH-RH propargylamide by conversion to the azide and reaction with allylamine and propargylamine, respectively. LH and FSH levels were measured over a 4-hr period after subcutaneous injection of these two peptides into immature male rats in order to detect any prolongation of activity. The allylamide analog was quite active, releasing 1.7 times more LH and 1.3 times more FSH than the same dose of LH-RH. The propargylamide analog was considerably less active, exhibiting 50% LH-releasing activity and 64% FSH-releasing activity. Neither peptide appeared to be longer acting than LH-RH.

Response of Luteinizing Hormone and Follicle-Stimulating Hormone to Different Doses of Synthetic Luteinizing Hormone-Releasing Hormone by Intramuscular Administration in Normal and Oligospermic Men: Preliminary Report

The response of LH and FSH levels to intramuscularly administered synthetic LH-RH was studied in two healthy volunteers and three oligospermic patients. Four tests with 50, 100, 250, and 500 mug of LH-RH, respectively, were carried out on each subject at 8 am; the interval between tests was one week. The serum levels of LH and FSH were determined by radioimmunoassay (double-antibody method) before each injection, and 60, 120, 180, and 240 minutes after each injection. No differences in the basal values of either hormone were observed. In both oligospermic and normal men, maximal responses were obtained with doses between 100 and 250 mug. With 500 mug, levels decreased rather than increased. Maximal peaks occurred between 60 and 180 minutes after injection. In the two normal subjects, the responses of LH and FSH were similar. Two of the three oligospermic patients showed discordant responses. From the results, we can assume that LH-RH doses between 100 and 250 mug should be used as a basis for chronic treatment.

Synthesis and biological activity of LH-RH analogs modified at the carboxyl terminus.

Des(Pro9,Gly10)-LH-RH ethylamide, des(Pro9,Gly10)-LH-RH butylamide, desGly10-LH-RH 2-aminoethylamide, and desGly10-LH-RH hydrazide were synthesized by a solid-phase method involving cleavage of protected peptide intermediates from their resin support by reaction with ethylamine, butylamine, ethylenediamine, and hydrazine, respectively. In the assay utilizing steroid pretreated, ovariectomized rats, the peptides were found to have the following LH-releasing activities when compared with natural LH-RH: ethylamide, 0.2%; butylamide, 0,1%; 2-aminoethylamide, 2.4%; hydrazide, 12%. DesGly10-LH-RH hydrazide was used as a precursor in the synthesis of desGly10-LH-RH allylamide and desGly10-LH-RH propargylamide by conversion to the azide and reaction with allylamine and propargylamine, respectively. LH and FSH levels were measured over a 4-hr period after subcutaneous injection of these two peptides into immature male rats in order to detect any prolongation of activity. The allylamide analog was quite active, releasing 1.7 times more LH and 1.3 times more FSH than the same dose of LH-RH. The propargylamide analog was considerably less active, exhibiting 50% LH-releasing activity and 64% FSH-releasing activity. Neither peptide appeared to be longer acting than LH-RH.

Measurement of rat LH with a double-antibody solid-phase radioimmunoassay: effect of LH-RH and of testosterone oenanthate in castrated animals.

A double-antibody solid-phase radioimmunoassay for the measurement of rat LH was described. The use of a solid-phase method for the second incubation resulted in a considerable saving of time as compared to the conventional double-antibody method. The sensitivity and accuracy of the method were not affected by this modification. It was found that there was a cross-reaction between the NIAMD-anti-rat-LH-serum-1 used and NIAMD-rat-FSH-RP-1. This indicates that the test system does not specifically measure rat LH but gonadotrophic activity. The RIA was tested under different experimental conditions. In male rats, the effect of castration and of subsequent treatment with testosterone oenanthate upon serum LH, and upon the weight of the seminal vesicles, the ventral prostate, and the levator ani, was examined. Serum LH rose rapidly after castration and reached 2 to 4 weeks after orchidectomy a maximum (8-9 fold increase). Subsequent treatment with testosterone oenanthate caused a rapid decrease of serum LH. The accessory sex organs showed reciprocal changes of weight. In oophorectomized rats whose pituitaries had been blocked with oestradiol monobenzoate and progesterone, a linear log-dose response of plasma LH was found after administration of various doses of synthetic LH-RH.

Modification of in vitro neurotransmitter release from rat brain slices by hypophyseotropic factors

This chapter discusses the ultrashort feedback effects of releasing hormones. Previous experiments had indicated that the subcutaneous administration of crude hypothalamic extracts containing follicle-stimulating hormone–releasing hormone (FSH-RH) and devoided of any FSH and sex steroid contamination may bring about a significant reduction of FSH-RH stores in the hypothalamus of castrated, hypophysectomized rats. These experiments suggested the possibility that the brain might contain receptors sensitive to circulating levels of FSH-RH, and that FSH-RH might directly regulate its own production via an “ultrashort” feedback effect. Subcutaneous or intracarotid treatments with repeated doses of synthetic LH-RH are able to bring back to normal the elevated levels of hypothalamic LH-RH in castrated, hypophysectomized animals. The data support the view that releasing hormones have direct effects on the brain and speak in favor of the existence of “ultrashort” feedback mechanisms controlling gonadotropin secretion In addition, the chapter also provides information on the modification of in vitro neurotransmitter release from rat brain slices by hypophyseotropic factors.

Circulating luteinizing hormone and testosterone response in rams after luteinizing hormone releasing hormone treatment.

ABSTRACT The relationship between the secretions of LH and testosterone after LH-RH administration was tested in entire rams. Three groups of two rams received, intravenously, 100 μg; 800 μg LH-RH in single injection; or 100 μg × 7 injections at half-hour intervals respectively and samples were collected every 10 or 20 min for 6 hours. Plasma LH and testosterone were assayed by radioimmunoassay. The quantity of LH released following 800 μg LH-RH was higher than released after 100 μg LH-RH and there was a positive correlation between the total amount of LH released after LH-RH and the amount of testosterone released. It seems probable that the pre-injection level of testosterone regulates in a quantitative manner the effect of a given dose of LH-RH. In the case of successive injections of LH-RH, the plasma LH rose to a plateau but the last two treatments failed to prevent the decline in the level of LH. This suggests that testosterone, still high at the time, directly blocked the effect of LH-RH at the level of the pituitary.

Direct inhibition of pituitary LH secretion in rats by CB-154 (2-Br-alpha-ergocryptine).

The effect of 2-Br-α-ergocryptine Prolactin, LH and FSH were determined by (CB-154) on pituitary response to synthetic LH-double-antibody solid-phase radioimmunoassays. RH or rat hypothalamic extract (HE) was in-Serum prolactin levels were significantly de- vestigated in ovariectomized, estrogen-proges-creased by CB-154. Although the ergot alkaloid terone-blocked rats by measuring pituitary contentid not significantly change serum FSH levels, it and serum concentration of prolactin, LH and significantly suppressed LH release induced by FSH. CB-1S4 was injected once ip at a dose of synthetic LH-RH or rat HE. This suggests that 500 µ.g/100 g body weight 2 hr before autopsy or iv injection with synthetic LH-RH or rat HE. Prolactin, LH and FSH were determined by double-antibody solid-phase radioimmunoassays. Serum prolactin levels were significantly decreased by CB-154. Although the ergot alkaloid did not significantly change serum FSH levels, it significantly suppressed LH release induced by synthetic LH-RH ...

The effect of estradiol benzoate on the pituitary responsiveness to LH-RH in male and female rats.

Serum LH levels in male and female rats were estimated immediately before and 5, 10 and 20 min after the administration of a standard dose of LH-RH. The effect of estradiol given 3 or 27 h prior to LH-RH was studied. Females were injected with estradiol benzoate on the 1st or 2nd day of diestrus. After an interval of 3 h, the response to LH-RH was blocked in both males and females. In the females, after 27 h the LH levels were high and LH-RH caused an extremely large further increase. In the males, after 27 h the response to LH-RH had returned, although the rise in serum LH was still much smaller than that seen in the estradiol-pretreated females.

Unaltered plasma prolactin levels in men after administration of synthetic LH-releasing factor.

Plasma prolactin levels were not consistently changed by administration of a dose of synthetic LH-RH which released LH and, to a lesser extent, FSH in 19 normal men. Pretreatment with large doses of estrogen, progesterone, or their combination for three days did not affect the release of prolactin.

Effects of synthetic LH-RH and its analogs on rat anterior pituitary cyclic AMP and LH and FSH release

Synthetic LH-RH (1 μg/ml) in vitro increased cyclic AMP concentration of rat anterior pituitary within 1 min and HL release into the medium after 15 min incubation. The minimum effective dose of synthetic LH-RH on cyclic AMP formation was 10 ng/ml. Data obtained using synthetic analogs of LH-RH indicated that the N-terminal amino acid and the C-terminal carboamide group of synthetic LH-RH are necessary for biologic activity.

LH synthesizing activity of synthetic LH releasing hormone assessed by rat pituitary implanting system of rat intratesticular test.

LH synthesizing activity of synthetic LHRH was proved by using the rat pituitary implanting system of the rat intratesticular test which the authors had previously proposed for the evaluation of LH releasing factor. In this test system, administration of a very low dose of LHRH (0.1 ng) gave a definite positive response within 1 hr.

Release of luteinizing hormone by synthetic LH-releasing hormone in the ewe and ram.

SummaryLarge or small doses of synthetic LH-RH were injected into the carotid artery or intramuscularly in three anestrous ewes and one vasectomized ram. Intracarotid injection of 5 pg of synthetic LH-RH elicited monophasic responses in LH-release; the highest levels of serum LH were reached within 5-10 min after injection of LH-RH, followed by a gradual decrease. Injection of 250 pg of LH-RH resulted in a rise of serum LH within 5-10 min which was indistinguishable in magnitude from that after 5 pg of LH-RH. These levels remained steady or kept rising very gradually for 25 rnin or longer, then again started rising sharply. The peak levels were observed at 1.5 hr after injection, followed by a gradual decrease. Four hours after injection of LH-RH, serum LH levels were still higher than during the preinjection levels. Intramuscular injection of a large dose of LH-RH elicited patterns similar to those observed following intracarotid injection of LH-RH. The magnitude of response after intramuscular injection...