Doses Of LH Research Articles

Effects of exogenous LH or FSH on endogenous FSH, progesterone and estradiol secretion.

In one set of experiments, an ovulatory dose of ovine LH or FSH was injected, on the afternoon of proestrus, into rats which had received pentobarbital (PB). Serum FSH was elevated over noninjected controls at 1000 h estrus. The adrenal glands were not necessary for this response. Ovariectomy, performed shortly before the gonadotrophin injection, caused an elevation in serum FSH the following morning, which was not further increased by the injection of LH or FSH. Serum LH was not elevated nor was pituitary LH content decreased at 1000 h estrus in any treatment group. In a second set of experiments, the time course of LU, FSH, estradiol (E2) and progesterone (P4) was investigated, between proestrous afternoon (1630 h) and estrous morning (1000 h), in 3 treatment groups: a) saline controls (no PB), b) PB controls (no LH), c) PB + LH (8 μg IV at 1530 h). a) Saline controls showed a maximum LU and FSU primary surge at 1830 h; LH returned to baseline by 2300 h, while FSH fell slowly through the night. P4 was elevated at 1830 hand 2300 h, then fell to baseline; E2 fell abruptly between 1630 h and 1830 h. b) In PB controls, serum LH and P were continuously low, but a small rise in FSH occurred at 2300 h and 0400 h (estrus). E2 fell significantly also, but not as low as in the saline controls. c) LH, superimposed on PB, raised LH at 1630 h, but no further rises occurred, while FSH rose gradually to peak at 0400 h and then fell part way to saline control levels by 1000 h estrus. Thus, FSH appeared to be released independently of LU. The injected LU also induced a rise in P4 at 1630 h and 1830 h, with E2 falling, as in saline controls, between 1630 h and 1830 h. In a third experiment, P4 injection was tested, superimposed on PB blockade. P4 failed to increase LH or FSH (in a manner resembling LH injection), but did cause E2 to fall. It is concluded that the primary LH (and/or FSH) surge, as well as exogenous LH or FSH superimposed on PB blockade, can induce a release of FSH independently of changes in measured steroids (serum P4, E2) and in the absence of concomitant LH release. The induction of FSH release could not be detected in the absence of the ovary, but ovariectomy by itself increased FSH release without LH release. The data suggest that gonadotrophins, as well as ovariectomy, may induce FSH release by altering a nonsteroidal feedback from the ovaries.

Steroidogenesis by enzyme-dispersed turtle ( Chrysemys picta) ovarian cells in response to ovine gonadotropins (FSH and LH)

Follicular cells obtained by collagenase dispersion of turtle ( Chrysemys picta) ovarian tissue at three different times of the year (summer, stage 1; fall, stage 2; spring, stage 3) were examined for steroid (progesterone, testosterone, estradiol) secretion in response to increasing concentrations of ovine FSH and LH. At all three stages of the cycle FSH stimulated steroid production. Although both progesterone and testosterone were secreted by cells obtained from ovaries at stages 1 and 2 of the cycle, estradiol could not be detected in incubations of cells at these times. However, at stage 3 of the cycle, a stimulatory effect of FSH on estradiol production was apparent. The slight stimulatory effect of high doses of LH on progesterone and testosterone production may be due to FSH contamination in this particular NIH preparation. Turtle luteal cells prepared by the same method secreted progesterone in response to dibutyryl cyclic AMP.

Decreased fructose concentrations in coagulating glands of prepuberal rats treated with testosterone and LH.

Doses of testosterone propionate from 2.5 to 320 microgram and doses of LH from 2 to 360 microgram given over 1--3 days generally decreased fructose/body weight ratios in the coagulating glands of late prepuberal rats. The ratios of testes, seminal vesicles, coagulating glands and ventral prostates to body weight were increased after different treatment regimes with testosterone propionate. These changes in the variables measured could be detected by computer analysis in spite of the rapid growth rates of organs of rats of this age. LH increased the weights of only the seminal vesicles and coagulating glands, and then, only at the highest doses given.

CYCLIC AMP AND CYCLIC GMP ACCUMULATION IN HAMSTER PRE-OVULATORY FOLLICLES STIMULATED WITH LH AND FSH

Cyclic AMP and cyclic GMP accumulation in hamster pre-ovulatory follicles was determined after in vitro stimulation by LH and FSH. Combined time course and dose response experiments determined that the acute response of the follicles (0-30 min) to LH and FSH was similar with respect to cyclic AMP accumulation. The pattern of cyclic GMP accumulation was, however, distinctly different in LH and FSH stimulated follicles. LH increased follicular cyclic GMP only at the lowest dose (0.005 IU/ml), while higher doses of LH had no effect. In contrast, FSH at all doses stimulated cyclic GMP accumulation. The different cyclic AMP to cyclic relationships generated in the follicles by LH and FSH may be determinants in specificity of hormone action in pre-ovulatory follicles.

FSH and LH stimulation of ornithine decarboxylase activity: studies with porcine granulosa cells in vitro.

Under defined conditions in vitro FSH and LH caused a dose-dependent stimulation of ornithine decarboxylase (ODC) activity in granulosa cells isolated from porcine ovarian follicles. In cells from small follicles, FSH was at least twice as potent an inducer of the enzyme activity as LH. The cells from medium-sized follicles were more responsive to both hormones than cells from small follicles. In addition, the cells from medium-sized follicles were approximately equally responsive to maximal FSH and LH stimulation. Incubation of cells from either small follicles or medium-sized follicles with maximum effective doses of LH plus FSH caused no additive effects.

In vitro stimulation of 5 α-dihydrotestosterone and testosterone secretion from bullfrog testis by nonmammalian and mammalian gonadotropins

In vitro androgen secretion by bullfrog (Rana catesbeiana) testis was studied using mammalian and nonmammalian gonadotropins, including those from the bullfrog. LH from bullfrog, salamander, turtle, alligator, and sheep increased secretion of 5α-dihydrotestosterone (DHT) and testosterone (T) into incubation medium; Rana and ovine FSH preparations were inactive except at relatively high concentrations. Rana FSH, ovine PRL, and bovine GH did not influence LH-induced steroid secretion. Rana LH was about 3–10 times more potent than other nonmammalian LH preparations, and 30–50 times more potent than NIH-ovine LH. Dose-response characteristics were dependent upon incubation time and temperature. More DHT than T was present in incubation medium at all times and temperatures studied, and during all seasons. Contents of DHT and T in incubation medium were highly correlated, and the ratio increased with time and with dose of LH. These data support in vivo observations and indicate that DHT is a major testicular androgen in the bullfrog, stimulated specifically by LH. Control of testicular androgen secretion by LH may represent the ancestral tetrapod condition.

Regulation of Gonadotropin Receptors by Luteinizing Hormone in Granulosa Cells1

In association with luteinization, LH induces a decrease in the content of receptors for FSH and LH and an increase in that for PRL. To elucidate if the mechanism by which LH regulates its own receptors involved occupancy of sites and/or loss of receptors the effects of a luteinizing dose of LH were examined in the preovulatory follicles of immature hypophysectomized rats primed with estradiol and FSH. The measurable LH receptor content declined by 82% 24 h after LH administration. Serum concentration of the hormone declined by 24 h to 1.4% of the concentration measured 2 h after LH administration. Administration of iodinated LH to demonstrate occupancy of sites in vivo, resulted in a decline in the amount of hormone bound in vivo, over a period of time. This decline in occupancy paralleled the decrease in the number of available sites as measured in vitro. Furthermore, a large dose of highly purified hFSH administered in lieu of LH induced luteinization and an associated loss of gonadotropin receptors. These results indicate that luteinizing doses of LH and FSH induce a loss in gonadotropin receptors by mechanisms other than occupancy.

Serum 5α-Androstane-3α,17/3-Diol, Androsterone, and Testosterone Concentrations in the Male Rat. Influence of Age and Gonadotropin Stimulation

Serum concentrations of testosterone plus dihydrotestosterone (T-DHT), 5α-androstane- 3α, 17β-diol (Diol) and androsterone were measured during sexual maturation in male rats. Diol concentrations of 1 to 2.25 ng/ml were found in animals 10–90 days of age with no significant changes. Diol was the major androgen (5.75-8 times T-DHT) from age 20–40 days. Androsterone rose to 1.25 ng/ml at 25 days of age and declined to values of <0.5 ng/ml from age 30–90 days. Testosterone-DHT levels were 1 ng/ml or less from 10–40 days of age, and then rose to a peak at 60 days. The ratio of Diol to T-DHT was significantly elevated from age 20–35 days, indicating that Diol is the major androgen in circulation at this time. Acute treatment of 33 day old rats with LH, but not with FSH, resulted in a dose-dependent increase in serum T-DHT, Diol, and androsterone. The dose-response and time course of response for the three steroids were nearly identical. Changes in testes capacity to secrete androgens were assessed at 25, 33, 40 and 60 days of age by administering a maximum dose of LH before blood collection. Maximum response (sum of androsterone, Diol and T-DHT) occurred at 40 days with no further increase at 60 days.

Serum 5alpha-androstane-3alpha,17beta-diol, androsterone, and testosterone concentrations in the male rat. Influence of age and gonadotropin stimulation.

Serum concentrations of testosterone plus dihydrotestosterone (T-DHT), 5 alpha-androstane-3 alpha, 17 beta-diol (Diol) and androsterone were measured during sexual maturation in male rats. Diol concentrations of 1 to 2.25 ng/ml were found in animals 10-90 days of age with no significant changes. Diol was the major androgen (5.75-8 times T-DHT) from age 20-40 days. Androsterone rose to 1.25 ng/ml at 25 days of age and declined to values of greater than 0.5 ng/ml from age 30-90 days. Testosterone-DHT levels were 1 ng/ml or less from 10-40 days of age, and then rose to a peak at 60 days. The ratio of Diol toT-DHT was significantly elevated from age 20-35 days, indicating that Diol is the major androgen in circulation at this time. Acute treatment of 33 day old rats with LH, but not with FSH, resulted in a dose-dependent increase in serum T-DHT, Diol, and androsterone. The dose-response and time course of response for the three steriods were nearly identical. Changes in testes capacity to secrete androgens were assessed 25, 33, 40 and 60 days of age by administering a maximum dose of LH before blood collection. Maximum response (sum of androsterone, Diol and T-DHT) occurred at 40 days with no further increase at 60 days.

HYPOTHALAMIC, PITUITARY AND TESTICULAR FUNCTION DURING SEXUAL MATURATION OF THE MALE RAT

Hypothalamic content of gonadotrophin-releasing hormone (GnRH), serum LH and FSH, capacity of the testis to synthesize testosterone in vitro, and testicular 5-ene-3 beta-hydroxysteroid dehydrogenase-isomerase and 17 beta-hydroxysteroid dehydrogenase were measured in groups of rats at approximately 5 day intervals from birth to day 64 and at days 74 and 89. The capacity of the testes to synthesize testosterone in vitro was measured in the presence of a saturating dose of rat LH. Gonadotrophin-releasing hormone increased steadily from 0-17 ng per hypothalamus at birth to a maximum of 7 ng at day 52 and then remained constant. LH concentrations were highly variable and often exceeded adult values between days 10 and 32. After day 32 a steady rise was observed which reached adult values between days 37 and 42. FSH concentrations markedly increased from 255 ng/ml observed at birth and day 10 to a peak value of 1000 ng/ml at day 32. Subsequently there was a steady decline in FSH values until day 74 when the concentration returned to values found at birth. 5-ene-3 beta-Hydroxysteroid dehydrogenase-isomerase activity exhibited a rapid increase between days 12 and 19 followed by an even greater rate of increase between days 19 and 32 when adult levels were attained. 17 beta-Hydroxysteroid dehydrogenase activity was very low between birth and day 22. Enzyme activity began to increase at day 22 with a rapid increase in activity observed between days 37 and 58. The increase in capacity to synthesize testosterone closely followed the increase in 17 beta-hydroxysteroid dehydrogenase activity. The study demonstrates that during sexual maturation in the male rat, changes in serum LH and FSH do not reflect changes in hypothalamic GnRH. The appearance of Leydig cells as monitored by 5-ene-3 beta-hydroxysteroid dehydrogenase-isomerase activity precedes by approximately 20 days the increase in testicular capacity to synthesize testosterone in vitro. The latter coincides with the increase in 17 beta-hydroxysteroid dehydrogenase activity. These results suggest that 17 beta-hydroxysteroid dehydrogenase is a limiting factor in the ability of the testis to respond to LH stimulation.

Ovulation in light-estrous rats induced by darkness.

Adult female rats show continual vaginal cornification and cease ovulation a few weeks after they are exposed to continuous lighting (light-estrous rats). When these rats were placed in the darkness for 10 hr, 80% of the animal ovulated approximately 46 hr later. Peripheral LH increased to a small peak immediately after placing in darkness concomitant with a decrease in pituitary LH content; a large peak, 20 times higher than the basal LH level, was observed at 20 to 22 hr. Progesterone concentration in ovarian vein blood remained at extremely low levels while estrogen levels tended to rise after small LH peak. This estrogen rise appeared to play an important role in inducing the main LH peak. Simulation of the small LH peak by low doses of exogenous LH succeeded in inducing ovulation of light-estrous rats in similar fashion to the exposure of light-estrous rats to 10-hr darkness. Therefore, the small amount of LH secretion observed after the initiation of the darkness-treatment may be considered as a trigger for the whole sequence of hormonal changes leading to ovulation.

Effects of prolactin on the sensitivity of the testis to LH.

Treatment of adult hypophysectomized rats with ectopic pituitary homografts caused a significant increase in testicular sensitivity to LH, as determined from measurements of peripheral testosterone levels 2.5 h after the injection of a single large dose of LH. Increased testicular responsiveness to acute LH stimulation was also observed after treatment with grafts or prolactin (PRL) combined with a chronic LH treatment, and in some instances, after treatment with PRL or chronic LH alone. It is suggested that PRL may have a role in sensitizing the testis to LH in the course of normal sexual maturation.

EFFECT OF AN OVULATORY DOSE OF LUTEINIZING HORMONE ON THE CONCENTRATION OF OESTRONE, OESTRADIOL AND PROGESTERONE IN THE RABBIT OVARIAN FOLLICLES

This study was done to determine the effect of an ovulatory dose of LH on the concentration of oestrone, oestradiol and progesterone in the follicular tissue and in follicular fluid of ovaries of sexually mature female rabbits. Eight animals were sacrificed without treatment while others (4 to a group) were sacrificed at 1, 3, 4, 6, 8 and 10 h after administration of LH (50 mug). In each animal follicles from both ovaries were pooled and the follicular tissue was separated from the fluid. Determination of oestrone, oestradiol and progesterone was done by radioimmunoassay separately in the follicular tissue and in fluid. One hour after LH treatment oestrogen levels were found elevated, as compared to the control, in the fluid but not in the tissue. Thereafter oestrogen levels declined and reached levels much below control at times nearing ovulation. On the other hand, progesterone levels were elevated over the control in both the tissue and fluid at 1 and 3 h. The tissue progesterone levels were, however, below control at and after 6 h. The sustained high concentrations of tissue progesterone in the earlier period after LH stimulation could play a role in the chain of events leading to follicular rupture.

The role of prostaglandins in the development of refractoriness to LH stimulation by graafian follicles

The possibility that prostaglandins might be responsible for the development of the pre-ovulatory refractoriness to the stimulation by LH of cyclic AMP accumulation in vitro in the Graafian follicle was examined. Isolated rabbit Graafian follicles were obtained at estrus and at 0.5, 5 and 9 hours after an ovulatory dose of LH. The follicles were incubated in vitro in the presence of [8- 3H]adenine and the accumulation of [8- 3H]cyclic AMP measured. Follicles from estrous animals responded to the in vitro addition of LH with a marked increase of cyclic AMP accumulation and lost this response as the time of ovulation approached. Animals pretreated with indomethacin, which inhibits the usual pre-ovulatory rise of follicular prostaglandin levels, showed essentially the same loss of responsiveness. Indomethacin alone was without effect. It is concluded that prostaglandins are not the major factor in the development of refractoriness to LH stimulation in vitro which has been observed in pre-ovulatory follicles.

Gonadotropin stimulation of in vitro progesterone production in reptilian and amphibian ovaries

The gonadotropic stimulation of progesterone production in vitro by preovulatory ovarian tissues from a chelonian reptile ( Chelydra serpentina), crocodilian ( Caiman sclerops), urodele amphibian ( Ambystoma tigrinum) and anuran amphibian ( Rana catesbeiana) was examined with a variety of mammalian and nonmammalian hormones, with emphasis on the homologous FSH and LH. In the turtle ovary, ovine (NIH) FSH was the most potent hormone while NIH-LH was relatively inactive. However, both FSH and LH from a turtle ( Chelonia mydas) and crocodilian ( Alligator mississipiensis) were effective; the two reptilian LHs appeared more potent than the FSHs. Similarly, both FSH and LH from the alligator and sheep effectively stimulated progesterone production by the Caiman ovary; in this case, Alligator-LH was the most potent steroidogenically. Results with postovulatory follicles and corpora lutea from the snapping turtle ( Chelydra) were similar to those for preovulatory tissues. FSH from sheep and Chelydra were more potent than the respective LHs. Ovine LH was especially inactive in these tissues, but the homologous LH stimulated significant progesterone production. In contrast, only LH (ovine and amphibian were tested) stimulated progesterone release from the two amphibian ovaries. Rana-LH was more potent than ovine LH in Rana. In Ambystoma, both progesterone secretion and ovulation were observed over a wide range of doses of homologous LH, but FSH was inactive in both regards. Ovulation was inhibited while progesterone was maximal at the highest doses of LH. These comparative data suggest that the “primitive” tetrapod condition involved a relatively high specificity for LH for the control of ovarian progesterone production. This LH-specificity was apparently lost during early reptilian radiation, at least by the time that the captorhinids diverged into the extant orders. Since FSHs from diverse species are active in reptiles (and reptilian LHs but not FSHs are active in amphibians), the sensitivity to FSH in the reptilian ovary is viewed as being due to an alteration in gonadal receptors rather than to a structural change in the reptilian FSH molecule.

Differential effects of male stimuli on follicle-stimulating hormone, luteinizing hormone, and prolactin secretion in prepubertal female mice.

Puberty may be induced rapidly in young female mice by exposing them to adult males. The relevant male stimuli include a urinary pheromone and tactile cues, the latter acting in a potentiating capacity. The specific action of the urinary pheromone on pituitary gonadotropins was the subject of the present research. Immature females of a standard size were either paired with adult males, isolated and their bedding sprayed with male urine, or maintained as isolated controls. Exposure to male urine resulted in a rapid and significant release of LH (30 min) which was maintained at an average of 50% higher than levels in isolated controls throughout the 48 h experiment; no immediate changes were observed in either serum FSH or prolactin, but FSH was depressed and prolactin rose progressively during later sampling periods. Cohabitation with an adult male yielded parallel but decidedly stronger reponses in the concentrations of all three hormones. Exogenous estrogen, administered in a second experiment at a dosage previously found to mimic the puberty-inducing action of a male, suppressed serum FSH and LH while elevating serum prolactin. Thus, the present results suggest a) that the male's urinary stimulus exerts its action on immature females via LH release with no immediate and/or direct effects on the other two tropic hormones, and b) that the delayed alterations in serum FSH and prolactin concentrations accompanying male- and/or urine-exposure are secondary consequences of an LH-induced release of estradiol. Attempts to induce the entire pubertal cycle in intact females with subovulating doses of LH, nevertheless, were unsuccessful.

Maintenance of spermatogenesis and seminal vesicles in the hypophysectomized catfish, Heteropneustes fossilis (Bloch): effects of ovine and salmon gonadotropin, and testosterone.

The effects of 20-day treatment with ovine luteinizing (LH) and follicle-stimulating hormone (FSH), partially purified salmon gonadotropin (SG-G100), and testosterone were investigated by evaluating the maintenance of spermatogenesis in the testes and secretory activity in the seminal vesicles of the catfish, Heteropneustes fossilis, after hypophysectomy during the prespawning period. Low doses of LH (0.1 or 1 μg per fish) neither maintained spermatogenesis in the testes nor secretory activity in the seminal vesicles, whereas a higher dose of LH (10 μg per fish) maintained spermatogenesis qualitatively, and sustained the seminal vesicles in a moderately secretory state. One microgram of SG-G100 per fish partially maintained spermatogenesis but the seminal vesicles showed poor maintenance. Ten micrograms of SG-G100 per fish not only sustained spermatogenesis qualitatively and quantitatively, but also induced spermiation; the seminal vesicles, though enlarged, contained little secretion, indicating possible reduction through spermiation. FSH did not maintain spermatogenesis in the testes or secretory activity in the seminal vesicles. Testosterone (10, 100, or 500 μg per fish) had a dose-dependent maintenance response in the testes and seminal vesicles; with 500 μg of testosterone the maintenance of testes and seminal vesicles was similar to that in initial intact controls, with no indication of spermiation.

The influence of mammalian and avian gonadotropins on in vitro ovarian steroid synthesis in the turtle ( Chrysemys picta)

The synthesis of steroids from 7α[ 3H]cholesterol and 7α[ 3H]pregnenolone by turtle ovarian tissues in vitro was studied. Pregnenolone, 17α-hydroxypregnenolone, progesterone, 17α-hydroxyprogesterone, androstenedione, testosterone, dehydroepiandrosterone, estrone, estradiol 17β, estriol, and 16-epiestriol were identified as products. All estrogens were detectable in incubates of preovulatory follicular tissue, but only small quantities of estrone were found in incubates of follicular tissue from postovulatory animals and luteal tissue. The effects of mammalian and avian gonadotropins on the metabolism of tritiated precursors were studied. Both mammalian and avian LH were stimulatory when conversion of cholesterol or pregnenolone to major steroid products was examined. In particular, enhancement of estrogen biosynthesis predominated in preovulatory follicular tissue, whereas increased progestin yield was the major effect in follicular and luteal tissue from postovulatory animals. The effects of FSH were minimal compared to the same dose of LH. Thus, a slight increase in estrogen yield was only noted when preovulatory follicular tissue was incubated with cholesterol and mammalian FSH, and neither mammalian nor avian FSH had an effect on pregnenolone conversion by follicles from postovulatory animals. Prolactin had no effect on luteal progesterone synthesis when used alone, but reduced the stimulatory effect of mammalian LH on progesterone synthesis. 11-Desoxycorticosterone was not found to be a product of the turtle ovary under normal conditions or after in vitro ACTH stimulation.

LH and FSH in serum after intramuscular administration of LH/FSH-releasing hormone in normal and hypogonadal men.

The increase in serum concentrations of LH and FSH after intramuscular administration of LH/FSH-RH was investigated in normal and hypogonadotrophic hypogonadal males. LH and FSH were measured by specific radio-immunoassays. To evaluate the appropriate dose of LH/FSH-RH for intramuscular administration different doses were administered and with 200 mu g an increase in LH and FSH was found comparable to the results obtained by other investigators using intravenous administration. After the initial studies a simple test including two determinations before LH/FSH-RH administration and one 60 min and 120 min after administration was developed and used in all cases. In 12 normal males a significant increase in the serum concentration of both LH and FSH was found averaging 381% and 148% respectively 60 min after 200 mu g LH/FSH-RH with a slight decrease in LH but not in FSH after 120 min. A positive response similar to that in normal men was observed in 11 hypogonadotrophic hypogonadal patients presenting different clinical pictures. This indicates that in all these patients the hypogonadotrophic state was due to a hypothalamic defect and not to a hypophyseal disorder.

The Effect of LH on Cyclic AMP and Progesterone in Rat OvariesIn vivo

LH injected into the abdominal vein of immature female rats increased ovarian cyclec AMP levels within 1 min, and the effect lasted at least 2 hr. In PMS stimulated rats, a maximal effect on cyclic AMP levels was obtained with 5 mug of LH 10 min after injection. Significant effects were obtained with as little as 0.1 mug. The minimum effective dose required to increase ovary cyclic AMP levels in proestrus rats was 0.05 mug of LH. While 0.01 mug did not affect cyclic AMP levels, an increase in ovary progesterone was found. In other experiments, the response of cyclis AMP to LH in vivo was greater in immature ovaries than in those from animals pretreated with PMS and hCG. Small increases in cyclic AMP levels were also seen with FSH in PMS and PMS + hCG treated animals and with prostaglandin E2 and prolactin in PMS treated rats. These results parallel, to some extent, previous results found in vitro, and show that very small doses of LH can stimulate ovary cyclic AMP increases in vivo.