Correlation of hypothalamic LHRH, pituitary LH and plasma LH in developing rats.

Hypothalamic LHRH, pituitary LH and plasma LH levels were measured in rats of both sexes from day 5-60 after birth. The content of hypothalamic LHRH was very high in one-week-old male and female rats. It declined gradually till day 17 in the female rat and sharply on day 10 in the male rat. Subsequently the content of hypothalamic LHRH increased and showed peak values on day 25 in the female rat and on day 45 in the male rat. It decreased markedly at respective times of puberty in both sexes (day 37 in the female rat and day 52-60 in the male rat). Results of the study suggest that maturation of hypothalamo-hypophyseal-axis proceeds in three distinct stages. Observations on days 17, 25 and 37 in the female rat and on days 5, 7, 10 and 22 in the male rat clearly show an inverse relationship between hypothalamic LHRH and plasma LH and a parallel relationship between pituitary and plasma LH. Marked decline in the content of hypothalamic LHRH at respective times of puberty in both sexes indicates that the release of threshold levels of LHRH from the hypothalamus may apparently be the event initiating the pubertal changes in rat.     

Temporal relationship of the prolactin-dependent LH-induced LH receptor to the LH stimulus

The time course for LH induction of luteinizing hormone (LH) receptors as reflected in binding of ¹²⁵l-labeled hCG was investigated in hypophysecto-mized adult male rats. A low dose of oLH (10 μg) was administered to hypophysectomized adult male rats following pretreatments with prolactin, follicle-stimulating hormone (FSH), growth hormone (GH), or saline. Testicular binding of hCG was determined at different times following the LH injection using Leydig cell membrane preparations from a testicular homogenate. Seven days after hypophysectomy, hCG binding was at a nadir of 19 ± 7% (mean ± SD) of control values. Pretreatment with prolactin (100 μg/day) for 7 days was associated with a nonsignificantly different hCG binding that was 30 ± 5% of control values. Prolactin pretreatment plus a single 10 μg LH i.p. injection increased ¹²⁵l hCG binding up to 56 ± 10% of control values within 30 minutes of the LH injection. Luteinizing hormone-induced hCG binding persisted at a high level (51 ± 4% of control values) for 2 hours but returned to hypophysectomized control levels 6 hours after the i.p. LH injection. Seven days pretreatment with FSH or GH at 100 μg/day plus 10-μg LH injections was also tested. Neither FSH nor GH had a statistically significant effect on hCG binding nor could they mimic the ability of prolactin to allow for LH induction of hCG binding in the hypophysectomized adult male rats. These studies suggest that the induction or “up-regulation” of Leydig cell hCG binding by ovine LH is rapid and specifically dependent upon pre-exposure to prolactin.     

Effect of LH, FSH, LH + FSH and homoplastic pituitary extract on developing testis and epididymis of pigeon Columba livia

Ovine LH is needed for differentiation of juvenile Leydig cells and for their maintenance and steroidogenic potential, while FSH is necessary for Sertoli cell activity and spermatogonial multiplication suggesting that LH is steroidogenic hormone and FSH is gametogenic in the developing pigeon, C. livia. Homoplastic pituitary extract is more potent than ovine LH + FSH in stimulating gametogenic and endocrine components of the developing testis.     

Effect of neonatal castration on the content of hypothalamic LHRH, pituitary LH and plasma LH in developing male rats.

The content of hypothalamic LHRH and concentration of LH in pituitary and plasma were measured on day 5, 7, 10, 14, 17, 22, 25, 30, 45, 52 and 60 in male rats which were bilaterally castrated on day 2. The levels of plasma LH were significantly higher in all the groups of castrated rats than in normal male rats of corresponding ages. The concentration of plasma LH did not rise progressively but showed day to day fluctuation apparently due to alteration of sexual differentiation of the hypothalamus. The concentration of pituitary LH was significantly lower in neonatally castrated rats compared to normal male rats except on days 17, 25 and 30. The content of hypothalamic LHRH declined initially following castration, but from day 17 onwards significantly higher levels of hypothalamic LHRH were maintained in neonatally castrated rats than in intact control. Initial decline in the content of hypothalamic LHRH may be because of stimulation of release of LHRH which exceeds maximal rate of synthesis and subsequent increase in the content of hypothalamic LHRH may be due to enhanced LHRH synthesis as a result of castration.     

Effect of p-chlorophenylalanine on LH, FSH, prolactin and ovulation in the rat

The effect of p-chlorophenylalanine (PCPA: 300 mg/kg) on the rate of ovulation and plasma LH, FSH and prolactin secretion has been studied in rats at preovulatory periods (18th hour of diestrus) and post-ovulatory periods (9th hour of metaestrus). In both experimental groups, results showed that administration of PCPA caused an increase in both prolactin concentration and number of mature ovarian follicles (p less than 0.001). No changes were observed in FSH levels. LH concentration, however, decreased (p less than 0.001) and ovulation became totally inhibited. Rats treated at the 9th hour of metaestrus exhibited a marked luteinization as well as an increased number of corpus luteum in the ovaric tissue (p less than 0.001), whereas those treated at the 18th hour of diestrus underwent no luteinization and merely showed a greater number of mature ovarian follicles (p less than 0.001). PCPA, therefore, seems not to have a double effect on ovulation, LH, FSH, and prolactin secretion regardless of the pre or post-ovulatory periods. Changes observed in the ovaric tissue might be due to an increase in plasma prolactin concentration which appears earlier in the preovulatory than in the post-ovulatory treated animals. This difference may explain the double effect that has been attributed to the ovaric cycle and reproductive behavior.     

Mutants of Rhodobacter sphaeroides lacking one or more pigment-protein complexes and complementation with reaction-centre, LH1, and LH2 genes

The photosynthetic apparatus of Rhodobacter sphaeroides is comprised of three types of pigment-protein complex: the photochemical reaction centre and its attendant LH1 and LH2 light-harvesting complexes. To augment existing deletion/insertion mutants in the genes coding for these complexes we have constructed two further mutants, one of which is a novel double mutant which is devoid of all three types of complex. We have also constructed vectors for the expression of either LH1, LH2 or reaction-centre genes. The resulting system allows each pigment-protein complex to be studied either as part of an intact photosystem or as the sole complex in the cell. In this way we have demonstrated that reaction centres can assemble independently of either light-harvesting complex in R. sphaeroides. In addition, the isolation of derivatives of the deletion/insertion mutants exhibiting spontaneous mutations in carotenoid biosynthesis provides an avenue for examining the role of carotenoids in the assembly of the photosynthetic apparatus. We show that the LH1 complex is assembled regardless of the carotenoid background, and that the type of carotenoid present modifies the absorbance of the LH1 bacteriochlorophylls.     

LH and estradiol concentration in the blood and morphological characteristics of the hypothalamus, hypophysis and the ovaries of sheep after LH/FSH-RH and synthetic gestagen treatment

In the experiments the effect of synthetic LH/FSH-RH on the concentration of LH and estradiol 17-beta (E2) in the blood of sheep was followed during physiological anestrus, and the preovulatory LH release and the E2 level in the blood serum after the synchronization of estrus with chlormadinone acetate (CAP) were studied. Furthermore, the nuclear volumes of the neurons in the ncl. hypothalamicus anterior (NHA), ncl. paraventricularis (NPV), ncl. arcuatus (NARC) and the pars distalis ncl. mamillaris medialis (PD NMM) as well as the percentage numbers of the adenohypophyseal cells and the number of normal and atretic tertiary follicles of the same ewes are described. The results show that after synthetic LH/FSH-RH treatment the LH concentration gradually increases in the blood, intravaginally instilled CAP affects the hypothalamic neurons probably by increasing significantly the concentration of the endogenous E2 that sensitizes the receptors of the hypothalamo-hypophyseal structures to LH/FSH-RH, enhancing, thus, its effect. The changes in the nuclear volume of the neurosecretorial cells of the hypothalamus after the administration of the mentioned substances indicate an ultrashort feed back in the regulation of secretion and the LH/FSH-RH release by the NARC cells. The changes were considered from the viewpoint of influencing the estrous cycle and the productivity of ewes.     

Effects of exercise on the serum concentrations of FSH, LH, progesterone, and estradiol.

The effects of 30 min of exercise (74.1 +/- 3.0% (VO2), on the responses of progesterone (P), estradiol (E2), follicle stimulating hormone (FSH), and luteinizing hormone (LH) were investigated in 10 women. With such exercise significant increments occurred in P (37.6 +/- 9.5%) and E2 (13.5 +/- 7.5%) (P less than 0.05), whereas no changes were observed in FSH and LH (p greater than 0.05). Exercise in the luteal phase and during menses provoked similar changes in P, but E2 concentrations remained unchanged when exercise occurred during menses (p greater than 0.05). With 8-11 weeks of training the menstrual cycles were quite irregular and retesting of subjects in the same phase of the cycle was not possible. Yet, when subjects were retested after training, no changes occurred in P, E2 or LH (p greater than 0.05) but a decrement did occur in FSH (p less than 0.10). Thus, heavy exercise in untrained subjects provokes significant increments in ovarian hormones, whereas no such increments are observed in trained subjects exercising at the same absolute workload.     

Influence of gonadotropin-releasing hormone pulse amplitude, frequency, and treatment duration on the regulation of luteinizing hormone (LH) subunit messenger ribonucleic acids and LH secretion

The effects of GnRH pulse amplitude, frequency, and treatment duration on pituitary alpha and LH beta subunit mRNA concentrations were examined in castrate-testosterone replaced male rats. Experimental groups received iv GnRH pulses (5, 25, or 125 ng) at 7.5-, 30-, or 120-min intervals for 8, 24, or 48 h. Saline pulses were given to control rats. Acute LH secretion was measured in blood drawn before and 20 min after the last GnRH pulse. In saline controls, alpha and LH beta mRNAs (150 +/- 14, 23 +/- 2 pg cDNA bound/100 micrograms pituitary DNA) fell to 129 +/- 14 and 18 +/- 2, respectively, after 48 h. In animals receiving GnRH pulses (7.5-min intervals), the 125-ng dose stimulated a slight increase (P less than 0.01) in alpha mRNA levels after 8 and 24 h and both LH subunit mRNAs were increased by the 25- and 125-ng doses after 48 h. The 30-min pulse interval injections (25- and 125-ng doses) increased LH beta mRNA levels after 8 h, but alpha mRNAs were not elevated until after 24 h. Maximum (3-fold) increases in alpha and LH beta mRNAs were seen in rats receiving 25-ng pulses every 30 min for 48 h. Using 120-min pulses, LH subunit mRNAs were not increased by any GnRH dose through 48 h. Acute LH release was not seen in rats receiving 5 ng GnRH pulses at any pulse interval.(ABSTRACT TRUNCATED AT 250 WORDS)     

On the correlation between FSH, LH and prolactin serum levels.

In 188 males FSH, LH, and prolactin serum levels determined from a single blood sample were found to be closely correlated. No correlation appeared to testosterone levels. The same correlation is observed, if serum levels of FSH, LH, and prolactin are measured after stimulation with LH-RH and TRH. In order to explain the close correlation, in five young men hormone levels were measured at 2-min-intervals over a period of 2 hours. Peaks of prolactin often correspond to those of FSH and LH, and a statistical correlation was found in two cases between FSH and prolactin. Results suggest a common releasing mechanism, which is superposed to the main mediating mechanism.     

Controlling interrelationships of progesterone/LH and estradiol/LH in mares

The interrelationships of progesterone, estradiol, and LH were studied in mares (n=9), beginning at the first ovulation (Day 0) of an interovulatory interval. An increase in mean progesterone concentrations began on Day 0 and reached maximum on Day 6, with luteolysis beginning on Day 14. A common progesterone threshold concentration of about 2 ng/ml for a negative effect on LH occurred at the beginning and end of the luteal phase. Progesterone and LH concentrations decreased at a similar rate from Day 6 until the onset of luteolysis on Day 14, consistent with a decreasing positive effect of LH on progesterone. Concentrations of LH during the increase in the ovulatory surge consisted of two linear regression segments involving a rate of 0.4 ng/ml/day for Days 14-22 and 1.8 ng/ml/day for Day 22 to 1 day after the second ovulation. The end of the first segment and beginning of the second segment was 2 days before ovulation and was the day the ovulatory estradiol surge was at a peak.     

Conjugation-length dependence of the T1 lifetimes of carotenoids free in solution and incorporated into the LH2, LH1, RC, and RC-LH1 complexes: possible mechanisms of triplet-energy dissipation

In addition to the roles of antioxidant and spacer, carotenoids (Cars) in purple photosynthetic bacteria pursue two physiological functions, i.e., light harvesting and photoprotection. To reveal the mechanisms of the photoprotective function, i.e., quenching triplet bacteriochlorophyll to prevent the sensitized generation of singlet oxygen, the triplet absorption spectra were recorded for Cars, where the number of conjugated double bonds (n) is in the region of 9-13, to determine the dependence on n of the triplet lifetime. The Cars examined include those in (a) solution; (b) the reconstituted LH1 complexes; (c) the native LH2 complexes from Rba. sphaeroides G1C, Rba. sphaeroides 2.4.1, Rsp. molischianum, and Rps. acidophila 10050; (d) the RCs from Rba. sphaeroides G1C, Rba. sphaeroides 2.4.1, and Rsp. rubrum S1; and (e) the RC-LH1 complexes from Rba. sphaeroides G1C, Rba. sphaeroides 2.4.1, Rsp. molischianum, Rps. acidophila 10050, and Rsp. rubrum S1. The results lead us to propose the following mechanisms: (i) A substantial shift of the linear dependence to shorter lifetimes on going from solution to the LH2 complex was ascribed to the twisting of the Car conjugated chain. (ii) A substantial decrease in the slope of the linear dependence on going from the reconstituted LH1 to the LH1 component of the RC-LH1 complex was ascribed to the minor-component Car forming a leak channel of triplet energy. (iii) The loss of conjugation-length dependence on going from the isolated RC to the RC component of the RC-LH1 complex was ascribed to the presence of a triplet-energy reservoir consisting of bacteriochlorophylls in the RC component.     

Role of LH in luteolysis and growth of the ovulatory follicle and estradiol regulation of LH secretion in heifers

The role of LH in luteolysis and development of the ovulatory follicle and the involvement of GnRH receptors in estradiol (E2) stimulation of LH secretion were studied in heifers. A pulse of PGF_2α, as indicated by a metabolite, was induced by E2 treatment on Day 15 (Day 0 = ovulation) and LH concentration was reduced with a GnRH-receptor antagonist (acyline) on Days 15, 16, and 17. Blood samples were collected every 6 h on Days 14-17 and hourly for 10 h beginning at the Day-15 treatments. Four groups were used (n = 6): control, acyline, E2, and E2/acyline. The number of LH pulses/heifer during the 10 h posttreatment was greater (P < 0.0002) in the E2 group (2.3 ± 0.4, mean ± SEM) than in the acyline group (0.2 ± 0.2) and was intermediate in the E2/acyline group (1.4 ± 0.2). Concentrations of progesterone in samples collected every 6 h on Day 15 showed a group-by-hour interaction (P < 0.02); concentrations decreased in the acyline group but not in the control group. The 12 heifers in the combined acyline and E2/acyline groups had three follicular waves compared to two waves in 10 of 12 heifers in the combined control and E2 groups. Results (1) supported the hypothesis that LH delays the progesterone decrease associated with luteolysis, (2) supported the hypothesis that LH has a positive effect on the continued development and growth of the selected ovulatory follicle, and (3) indicated that E2 stimulates LH production through an intracellular pathway that involves GnRH receptors on the gonadotropes and a pathway that does not involve the receptors.     

Plasma progesterone, FSH and LH levels associated with implantation in the mouse

Measurement of plasma progesterone, LH and FSH were made every 6 h during the first 6 days of pregnancy in the mouse. Plasma progesterone and LH were low on day 1, minimum values being recorded at 24 h post coitus. Concentrations of both these hormones started rising during the second half on day 2 with the rise continuing during day 3 to a progesterone peak of 25 ng/ml early on day 4 and an LH peak of 37 ng/ml late on day 4. Levels of progesterone fell during day 4 and LH during day 5 to approximately half their respective peak values and then remained relatively constant over the remainder of the measurement period. Levels of FSH, which were high early on day 1 (180 ng/ml), fell sharply by midday with a small rise late in the day followed by a decline during day 2 to a minimum level of 2 ng/ml at 48 h post coitus. Early on day 3 FSH values rose to 120 ng/ml then fell to 50-60 ng/ml during the next 6 h and remained relatively stable at this level during days 4 and 5. It is suggested that LH is concerned with progesterone production and maintenance of the corpus luteum whilst FSH is concerned with the production of oestrogen required for implantation in this species.     

Serum FSH, LH and testosterone in the male rhesus following prostaglandin injection

Adult male rhesus were treated with PGE₂, PGF_2α or the 13,14-dihydro-15-keto metabolite of PGE₂ in a randomized crossover design. Serum concentrations of FSH, LH and testosterone were determined and compared to the respective values in the same uninjected animals. No significant changes were noted in controls or following the metabolite injection. FSH increased gradually for 4 hours after metabolite treatment. In contrast, injection of PGF_2α was followed by an abrupt (within 15 minutes) increase in LH and testosterone. FSH increased gradually in 2 of 3 treated animals. Injection of PGE₂ was followed by a similar abrupt increase in LH concentration. This was not always associated with a significant increase in testosterone or FSH. These results demonstrate that injections of PGE₂ or PGF_2α can change serum gonadotropin and testosterone concentrations in male rhesus monkeys, and that the effects of these two prostaglandins are qualitatively different.