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PubMed1988

[Placental growth hormone. Significance relative to growth hormone and lactogen hormone].

Normal human placenta secretes within maternal compartment a pregnancy associated protein, placental growth hormone (PGH). This entity, agonist of pituitary GH, appears responsible for the elevated IGF I blood levels observed in the mother during pregnancy, while pituitary GH is no longer secreted. PGH could thus play a significant role in the anabolic processes of pregnancy. The biochemical mechanism responsible for PGH production is the expression of the GH-V gene at the placental level. This has been demonstrated by the positive probing of GH-V mRNA in this tissue, by the establishment of the restriction map and sequence of its cDNA as well as by the NH2-terminal sequence determination of both 22 and 25K PGH forms. The positive aspect of this function for human reproduction gains weight in that a placenta deleted for the CS-A, GH-V and CS-B gene expresses alternative genes coding for protein similar or related to pituitary GH or hPL, respectively.

Amino Acid Sequence↗
PubMed1985

Regulation of growth hormone mRNA synthesis by 3,5,3'-triiodo-L-thyronine in cultured growth hormone-producing rat pituitary tumor cells (GC cells). Dissociation between nuclear iodothyronine receptor concentration and growth hormone mRNA synthesis during the deoxyribonucleic acid synthesis phase of the cell cycle.

3,5,3'-Triiodo-L-thyronine (T3) regulates the growth rate and GH production of cultured GC cells, a rat pituitary tumor cell line. We have previously demonstrated a parallel increase in cellular content of DNA and nuclear T3 and glucocorticoid receptors during the DNA synthesis (S) phase of the GC cell growth cycle. To determine the relationship between the increase in nuclear hormone receptors and GH production in S-phase cultures, we measured the synthesis rate of GH by pulse-labeling with [3H]leucine and immunoprecipitation as well as the relative concentration of GH mRNA by dot hybridization employing formaldehyde-treated cytoplasm and GH cDNA. Total protein synthesis was similar in S-phase and asynchronous cultures. However, in comparison to asynchronous cultures, S-phase cells had an increased GH synthesis rate, p less than 0.005 (from 13,430 +/- 609 to 19,150 +/- 1160 cpm/10(6) cells/2 h) and increased GH mRNA, p less than 0.001 (from 7.2 +/- 1.2 to 14.5 +/- 1.5 relative A units). The S-phase-associated augmentation in GH production did not appear to result from a decrease in ADP-ribosylation induced by 2 mM thymidine treatment which was utilized for the S-phase synchronization. To determine whether increased GH mRNA and GH synthesis in S-phase was associated with an increase in synthesis of GH mRNA, we measured the incorporation of [3H]uridine into GH mRNA by incubating partially synchronized S-phase cells with [3H]uridine and isolating 3H-labeled GH mRNA by hybridization to GH cDNA immobilized on nitrocellulose filters. Total RNA synthesis was similar in asynchronous, S-phase and G1 cell populations. However, the mean incorporation of [3H]uridine into GH mRNA of S-phase cultures was decreased to 52, 59, and 61% (counts/min of GH mRNA/10(6) cells), 49, 59, and 65% (ppm of total RNA), and 64 and 69% (ppm of poly(A)+ RNA) of asynchronous cultures. Our studies show further that the decrease in [3H]uridine incorporation into GH mRNA did not result from a cell cycle specific change in efficiency of hybridization or exclusively to an S-phase associated increased rate of degradation of GH mRNA. Thus, despite increased nuclear T3 and glucocorticoid receptors and, increased GH mRNA and GH synthesis, the synthesis rate of GH mRNA appears decreased in S-phase GC cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine Diphosphate Ribose↗
PubMed1976

Hormone-stimulated desensitization of hormone-dependent adenylyl cyclase. Dual action of luteninizing hormone on pig graafian follicle membranes.

Washed membrane particles from pig Graafian follicles larger than 6 mm in diameter were found to contain an adenylyl cyclase system that is highly responsive to luteinizing hormone (LH). Under the assay conditions used (1.5 mM ATP, 5 mM MgCl2, 1.4 mM EDTA, and 1.0 mM ethylene glycol bis(beta-aminoethyl)-N,N'-tetraacetic acid, pH 7.0) LH stimulated enzyme activity up to 7-fold. Half-maximal activation was obtained between 3 and 6 X 10(-10) M of added LH, provided the reaction was carried out under equilibrium conditions. In contrast to findings in large follicles, adenylyl cyclase activity was found to be unresponsive to LH in small immature follicles (1 to 2 mm in diameter) and partially responsive to LH (2- to 3-fold stimulation over basal) in follicles of medium size (3 to 5 mm in diameter). Washed membrane particles from follicles larger than 6 mm were found to contain also an ATP- and Mg2+-dependent process which, upon incubation at 30 degrees, causes the adenylyl cyclase system to lose its susceptibility to respond to LH. Because this loss of LH-stimulated activity was not accompanied by a concomitant loss of basal activity, it was concluded to be the expression of a desensitization reaction. Desensitization was almost undetectable at 5 mM total added MgCl2 and required, to be readily detectable, addition of MgCl2 concentrations in excess of 10 mM. LH was found to stimulate desensitization in the presence of 1 mM cyclic adenosine 3':5'-monophosphate by diminishing the requirement for MgCl2. Loss of LH-stimulated adenylyl cyclase activity was readily detectable at 5.0 mM total added MgCl2 in the presence of 10 mug per ml of LH. Half-maximal stimulation of desensitization by LH was found to occur at about 25 X 10(-10) M, i.e. at about 4 to 6 times higher concentrations than needed for half-maximal stimulation of adenylyl cyclase activity. Half-maximal LH-stimulated desensitization was obtained with 0.5 to 0.7 mM ATP in the incubation. Neither GTP, nor adenyl-5'-yl imidodiphosphate, the nonphosphorylating imidodiphosphate analogue of ATP, supported the desensitization reaction, suggesting that this process may be mediated via phosphorylation of one or more of the components of the adenylyl cyclase system. LH-stimulated desensitization was detected also in washed membrane particles derived from dissected rabbit Graafian follicles, whose adenylyl cyclase becomes desensitized in vivo within minutes after human chorionic gonadotropin injection (Hunzicker-Dunn, M., and Birnbaumer, L., Endocrinology, in press), but not in membrane particles from corpora lutea of pregnant or pseudopregnant rabbits, whose adenylyl cyclase becomes desensitized in vivo only several hours or days after human chorionic gonadotropin injection (Hunzicker-Dunn, M., and Birnbaumer, L., Endocrinology, in press). It is suggested that both actions of LH (stimulation of adenylyl cyclase and stimulation of desensitization) are receptor-mediated, and that neither of them is mediated by cyclic adenosine 3':5'-monophosphate...

Adenosine Triphosphate↗
PubMed1976

Leteinizing hormone and luteinizing hormone releasing hormone-like immunoreactivity in the jugular venous blood of sheep at various stages of the oestrous cycle.

Luteinizing hormone and LH-RH-like immunoreactivity were measured in the jugular venous plasma of Clun Forest ewes at various stages of the oestrous cycle. Blood samples were collected through jugular venous cannulae every 2 h for at least 20 days from three ewes during the breeding season. The ewes were checked twice daily for oestrus using a vasectomized ram. Plasma LH peaks of apparent height 112-192 ng NIH-LH-S17 equivalents/ml were detected at oestrus with basal levels of 2-15 ng/ml during most of the remainder of the 17-day oestrous cycle. Peaks of LH-RH-like immunoreactivity occurred at various times of the cycle. The apparent maximal level of these peaks was 220 pg/ml compared with basal levels of less than 10 pg/ml. Further ewes (two for each group) were sampled at 4 min intervals for 12 h, (1) from onset of oestrus, (2) 36-48 h after onset of oestrus or (3) on day 10 of the oestrous cycle. In the ewes sampled at oestrus, peaks of LH-RH-like immunoreactivity were detected before, during and after the preovulatory LH peak. Those detected after the LH peak were unassociated with any further increases in the plasma LH level. In the ewes sampled 36-48 h after onset of oestrus and on day 10 of the cycle, several peaks of LH-RH-like immunoreactivity unassociated with any increases in the LH level were detected. These peaks, and those detected at oestrus, had durations of only one or two samples, and in some cases reached levels of several ng/ml compared with basal levels of less than 10 pg/ml. The significance of these results is discussed.

Animals↗
PubMed2002

Growth hormone releasing hormone test for infertile men with spermatogenetic maturation arrest.

PURPOSE: Growth hormone has an important role in the function of the male reproductive system. We investigated infertile men with impaired growth hormone secretion. MATERIALS AND METHODS: Growth hormone status was studied in 8 fertile men and 9 infertile men with azoospermia due to spermatogenetic maturation arrest. Growth hormone releasing hormone, the specific stimulatory neurohormone, was used in the growth hormone stimulation test. A dose of 100 microg. of growth hormone releasing hormone was infused intravenously and serum growth hormone concentrations were measured at 0, 15, 30, 60, 90 and 120 minutes. Serum follicle-stimulating hormone, luteinizing hormone, prolactin, testosterone and estradiol were also measured before the test. RESULTS: Serum follicle-stimulating hormone concentrations were significantly increased in the azoospermic group and basal levels of growth hormone were similar to those in the control group. Serum growth hormone concentrations increased after injection of growth hormone releasing hormone and the levels of growth hormone peaked after 30 minutes in both groups. At time 30 minutes growth hormone levels had decreased significantly more in the azoospermic group than in the controls. Men with azoospermia due to spermatogenetic maturation arrest had a low response to the growth hormone releasing hormone test. CONCLUSIONS: Relative growth hormone insufficiency, which may be caused by reduced reactivity to growth hormone releasing hormone in pituitary growth hormone secretory cells, is strongly related to spermatogenic dysfunction.

Adult↗
PubMed1987

Specific luteinizing-hormone-releasing hormone receptor binding sites in hippocampus and pituitary: an autoradiographical study.

Using the iodinated luteinizing-hormone-releasing hormone analogue [D-Ala6, N alpha MeLeu7, Pro9 NEt]-luteinizing-hormone-releasing hormone as radioligand, specific binding sites have been visualized in the rat both in the pituitary and the hippocampal formation of the brain. In the hippocampus, the CA1, CA2 and particularly CA3 regions were heavily labelled. These hippocampal sites have a pharmacological specificity resembling that of luteinizing-hormone-releasing hormone receptors in pituitary homogenates and could therefore represent true luteinizing-hormone-releasing hormone receptors. The luteinizing-hormone-releasing hormone superagonist [D-Ala6, Pro9 NEt]-luteinizing-hormone-releasing hormone and the potent antagonist [D-pGlu1, D-Phe2, D-Trp3,6]-luteinizing-hormone-releasing hormone were highly potent in displacing the iodinated luteinizing-hormone-releasing hormone analogue. The weak agonist [Gln8]-luteinizing-hormone-releasing hormone, however, was at least two orders of magnitude less potent. Somatostatin was inactive. Hippocampal luteinizing-hormone-releasing hormone receptors were species-specific, being present in the rat but not in the mouse, guinea-pig, hamster, rabbit and human brains. In order to identify the cellular location of these hippocampal receptors, various lesions were performed. Electrolytic lesions of the septal afferents did not reveal any receptor density change. Colchicine as well as kainic acid injections did, however, reduce considerably the number of hippocampal receptors. Interestingly, in the electrolytically and kainic-acid-lesioned animals, the appearance of non-displaceable luteinizing-hormone-releasing hormone binding sites within a well-defined area corresponding to the lesioned, gliosis-rich area was observed. The present results suggest the presence of pharmacologically specific, species-dependent, luteinizing-hormone-releasing hormone receptors located, at least partly, on intrinsic hippocampal neurons, in particular granule and pyramidal cells.

Animals↗
PubMed2002

Antitumor effects of the cytotoxic luteinizing hormone-releasing hormone analog AN-152 on human endometrial and ovarian cancers xenografted into nude mice.

OBJECTIVE: Most human endometrial and ovarian cancers express receptors for luteinizing hormone- releasing hormone. These receptors can be used for targeted chemotherapy with cytotoxic luteinizing hormone-releasing hormone analogs such as AN-152, in which doxorubicin is linked to [D-Lys(6)]luteinizing hormone-releasing hormone. STUDY DESIGN: The antitumor effects of doxorubicin and AN-152 were assessed in vivo in human luteinizing hormone-releasing hormone receptor-positive HEC-1B endometrial cancers and NIH:OVCAR-3 ovarian cancers and in the luteinizing hormone-releasing hormone receptor-negative SK-OV-3 ovarian line. Nude mice bearing these tumors subcutaneously were injected intravenously with saline solution (control), AN-152, or doxorubicin at equimolar doses. Luteinizing hormone-releasing hormone receptor expression in tumors and specimens of human reproductive (n = 5) and nonreproductive (n = 15) normal tissues and in hematopoietic stem cells were analyzed with reverse transcriptase-polymerase chain reaction and radioligand binding assay. RESULTS: The tumor volumes of luteinizing hormone-releasing hormone receptor-positive HEC-1B and NIH:OVCAR-3 cancers were reduced significantly (P <.001) 1 week after treatment with AN-152 at 700 nmol/20 g or at 300 nmol/20 g. No toxic side effects were observed. Treatment with doxorubicin arrested tumor growth but did not reduce tumor volume. Doxorubicin at 700 nmol/20 g caused a high mortality rate and at 300 nmol/20 g (8.7 mg/kg) caused a loss of body weight, but no deaths occurred. The growth of luteinizing hormone-releasing hormone receptor-negative SK-OV-3 cancers was not affected by AN-152. Normal human nonreproductive tissues, hematopoietic stem cells, and vaginal tissue did not express luteinizing hormone-releasing hormone receptors, but luteinizing hormone-releasing hormone receptors were found in the ovary, fallopian tube, cervix, endometrium, and myometrium. CONCLUSION: Targeted chemotherapeutic luteinizing hormone-releasing hormone analog AN-152 is more effective and less toxic than cytotoxic radical doxorubicin on luteinizing hormone-releasing hormone receptor-positive tumors. AN-152 could be considered for targeted chemotherapy in patients with ovarian or endometrial cancers.

Animals↗
PubMed1987

Aging changes in synaptology of luteinizing hormone-releasing hormone neurons in male rat preoptic area.

This study was undertaken to examine some aspects of the anatomical substrate for reproductive senescence. Immunocytochemically identified luteinizing hormone-releasing hormone neurons and their processes in the male rat brain preoptic area were compared in young adult (2-4 months), middle-aged (12-14 months) and old (20-23 months) animals. At the light microscopic level there were no age-dependent differences in total numbers or sizes of LHRH neurons nor in their distribution in the brain. Examination of these neurons at the electron microscopic level did reveal significant differences in certain organelles and in the degree and kind of synaptic input. Random sections of middle-aged luteinizing hormone-releasing hormone neurons more frequently passed through the nucleolus and the incidence of nematosomes was higher than in luteinizing hormone-releasing hormone neurons from the young and old animals. Quantitative measures of synaptic input to luteinizing hormone-releasing hormone soma and dendrites as well as to unidentified neurons in the same thin section were made. These are reported as percent of membrane that showed synaptic structure. Dendrites of both luteinizing hormone-releasing hormone and nonidentified neurons were more densely innervated than perikarya. The density of synaptic input to luteinizing hormone-releasing hormone neurons was significantly greater than that to nonidentified neurons in young and middle-aged animals, but was equal to that of nonidentified neurons by old age. Age-related changes were noted in synaptic organization with the most significant change being an increased input to luteinizing hormone-releasing hormone perikarya. Indeed, synaptic input to luteinizing hormone-releasing hormone perikaryal membrane was increased three-fold by middle age and ten-fold by old age. Density of synaptic input to luteinizing hormone-releasing hormone dendritic membrane did not change with age. There were no aging changes in percentage of membrane with synaptic structure in nonidentified elements. Synapses were also classified on the basis of their synaptic vesicle content. There were proportionately more synaptic boutons containing round clear than pleomorphic vesicles in the young sample. The proportion of synapses with pleomorphic vesicles increased with age onto both luteinizing hormone-releasing hormone perikarya and their dendrites. The proportion of boutons containing some electron dense-core vesicles along with clear vesicles decreased with age onto both luteinizing hormone-releasing hormone and nonidentified neurons and their processes.

Aging↗
PubMed1986

Conversion of CSF monomeric growth hormone to large growth hormone with exposure to serum.

We have found a dissociation between CSF and serum growth hormone heterogeneity in a patient with suprasellar extension of a growth hormone-secreting pituitary tumour. When CSF was studied using gel chromatography, virtually all the growth hormone eluted as monomeric growth hormone with only 2.4% eluting before albumin as large growth hormone ('big, big' growth hormone). In contrast, the large component comprised 15.4% of the total immunoreactivity in simultaneously obtained serum. When the CSF specimen was incubated with growth hormone-poor serum, the elution pattern changed remarkably with 16% of the total immunoreactivity eluting as large growth hormone causing it to resemble the serum elution pattern. We also measured growth hormone heterogeneity in the inferior petrosal vein (a site very close to pituitary venous drainage) during inferior petrosal venography in 3 patients. As the growth hormone concentration increased, the percentage eluting as monomeric growth hormone increased, whereas that eluting as large growth hormone decreased. When the growth hormone concentration fell towards baseline, the percentage of growth hormone eluting as monomeric growth hormone fell while that eluting as large growth hormone increased. Thus, our studies suggest that large growth hormone results from binding of monomeric growth hormone to serum proteins or aggregation of monomeric growth hormone in the presence of protein. Our studies also show that when blood is sampled at a site close to the pituitary, the growth hormone is released primarily as monomeric growth hormone.

Blood Proteins↗
PubMed1976

Regulation of receptor concentration by homologous hormone. Effect of human growth hormone on its receptor in IM-9 lymphocytes.

When cultured human lymphocytes of the IM-9 line were exposed to human growth hormone (hGH) at 37 degrees, washed for 2 hours, and incubated with 125I-hGH, the binding of 125I-hGH was reduced. The magnitude of the reduction in binding was dependent on the concentration of growth hormone present as well as the duration of the exposure. As little as 2 X 10(-11) M (0.5 ng/ml) growth hormone had a discernible effect. Growth hormone at 2 X 10(-10) M (5.0 ng/ml), which is a low resting concentration of hormone in vivo and occupies about 20% of the receptors at steady state at 30 degrees, produced a 50% reduction in binding while 20 mg/ml, which occupies about 50% of the receptors under steady state conditions, produced an 80% loss of receptors. Further increases in growth hormone concentration produced little further effect on receptor loss. Thus, the loss of receptors at a given concentration of growth hormone (up to 20 ng/ml) in the preincubation at 37 degrees was greater than the occupancy produced by that concentration of growth hormone receptors under steady state conditions at 30 degrees. Analysis of the data indicated that the decrease in binding of 125I-hGH was due to a loss of receptors per cell without any change in affinity of receptor for hormone or in cell number. The concentration of insulin receptors on these cells was affected by the insulin concentration in the medium, and the concentration of growth hormone receptors was affected by growth hormone, but neither hormone had any effect on the heterologous receptors. Exposure of the cells to cycloheximide (0.1 mM) produced a progressive but smaller loss of growth hormone receptors, and the effect of cycloheximide was additive to the receptor loss induced by growth hormone, suggesting that cycloheximide inhibited synthesis of receptors while growth hormone accelerated loss of receptors. When growth hormone was removed from the medium, receptor concentrations were restored rapidly; half of the loss was restored by 6 to 8 hours and the full complement of receptors was restored by 24 hours following removal of the hormone. If the growth hormone was removed and replaced with cycloheximide, the return of the receptors was delayed until the cycloheximide was removed. Thus restoration of the receptors appeared to require the synthesis of new proteins. These data indicate that in the IM-9 lymphocytes the concentration of growth hormone receptors is very sensitive to regulation by growth hormone and also add further support to the suggestion that hormones in general actively regulate the concentration of their own receptors.

Animals↗
PubMed1993

Combined treatment with growth hormone and luteinizing hormone releasing hormone-analogue (LHRHa) of pubertal children with familial short stature.

We evaluated the 12 month growth of 18 pubertal children with familial short stature randomly assigned to clinical follow-up (group A), GH treatment alone (group B) and GH+LHRH analogue (LHRHa) treatment (group C). Height velocity increased significantly compared to baseline in groups A and B (4.7 +/- 0.4 vs 6.6 +/- 0.6 and 4.4 +/- 0.3 vs 8 +/- 1 respectively), but not in C (5 +/- 0.5 vs 6.5 +/- 0.4). Moreover in group B height and height prognosis standard deviation score SDS) also were higher (-2.2 +/- 0.2 vs -1.7 +/- 0.2 and 1.8 +/- 0.3 vs -1 +/- 0.2, respectively). Comparisons among the groups showed a significant increase in group B vs the other groups of height velocity SDS (3.9 +/- 1.3 vs 0.4 + 1 and 0.3 +/- 0.7) and of height prognosis SDS (-1 +/- 0.2 vs -2.4 +/- 0.3 and -2.4 +/- 0.3). In conclusion, after one-year treatment, GH seems to be more effective in stimulating growth than GH +/- LHRHa, even if studies of longer duration and/or follow-up are needed.

Adolescent↗
PubMed1989

Calcitonin suppresses growth hormone (GH) response to growth hormone-releasing hormone (GHRH) in man.

Calcitonin (CT) receptors have been found in the hypothalamus, suggesting a neuroendocrine role for this peptide. We have recently shown that, in the rat, central administration of salmon calcitonin (sCT) suppresses basal and GHRH-stimulated GH secretion. To further investigate how sCT alters GH secretion, we studied the effects of sCT (100U MRC, im) or placebo on basal and GHRH (50 micrograms, iv)-stimulated GH secretion in 6 normal men. GHRH was administered 1 h after sCT injection. Basal GH levels were not altered by sCT administration. However, GH response to GHRH was markedly suppressed by sCT (area under the curve - sCT: 574.6 +/- 69.7 vs placebo: 1057.2 +/- 284.8 micrograms. min/L; p less than 0.02). Cortisol levels were higher in sCT-treated subjects compared to controls, from 45 to 105 min after sCT injection (p less than 0.05). However, no correlation was found between GH response to GHRH and cortisol levels. No changes in glucose, calcium and PTH levels were seen. These results demonstrate that sCT inhibits GHRH-induced GH secretion in man by a mechanism apparently independent of changes in peripheral cortisol, glucose, calcium and PTH levels.

Adult↗