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M J Waters

Publications and source records attributed to M J Waters.

At least 109 records · Page 6Linked to original sources
PubMed1992

Growth hormone- and prolactin-binding proteins in mammalian serum.

The present study was undertaken to characterize the species specificity and diversity of lactogenic and somatogenic binding to serum among mammals and to classify GH-binding protein (GH-BP) in this group of species. Animal sera were characterized on the basis of human (h) GH and bovine (b) PRL binding levels, binding specificity toward GHs and PRLs, binding affinity constant (Ka), and the ability of a monoclonal antirabbit GH receptor antibody (MAb-7) to inhibit the binding to serum. Analyses of the results yielded a classification of the mammalian sera into five types of GH binding, which we elected to call GH-BP. The guinea pig had undetectable levels of GH-BP and was labeled type 0. Type I GH-BP was found in the mouse and the rat. hGH binding to GH-BP of type I serum was of low affinity (1.2-3.9 x 10(8) M-1) with high IC50 (approximately 100 ng/tube) and was purely somatogenic in nature. Type II GH-BP was found in the goat, sheep, and cow. Their IC50 of hGH binding was approximately 4-fold lower than that of type I GH-BP. Their binding of hGH was relatively specific and only marginally displaced by the PRLs. Type III GH-BP was found in the rabbit, horse, cat, dog, and pig. These animals' sera had high affinity binding toward hGH (4.7-9.2 x 10(9) M-1), with low IC50 (approximately 2 ng/tube) and dominant lactogenic binding. The great similarity of type III GH-BPs was further stressed by the ability of MAb-7 to inhibit [125I]hGH binding to all type III sera, but not to the other mammalian sera tested. Type IV GH-BP was found in the human and rhesus monkey sera. These were characterized by binding affinities that were intermediate between those for types II and III GH-BP and by the inability of nonprimate GHs to compete with hGH binding. To directly confirm the potent effect of the lactogenic hormones in type III GH-BP, the specific binding of bPRL to sera of type III animals was studied. [125I]bPRL-specific binding was determined under optimized assay conditions and was the highest in rabbit serum, with the following rank order being observed: rabbit >> horse = dog = pig > cat. Scatchard analysis of [125I]bPRL binding revealed linear plots with similar affinity constants (Ka) of 1.7-3.3 x 10(9) M-1.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Localization of the growth hormone receptor, identified by immunocytochemistry, in second trimester human fetal tissues and in placenta throughout gestation.

Pituitary GH secretion appears largely unnecessary for the attainment of normal birth size in many species, including man. This is believed to be due to an immaturity and/or an absence of GH receptors in many fetal tissues. However, in vitro studies using late first trimester human fetal tissues have demonstrated mitogenic actions of GH on liver and stimulation of insulin biosynthesis in pancreas. To resolve this discrepancy, we have employed immunocytochemistry to identify the presence and distribution of GH receptors in various human fetal tissues. Fetuses of 14-16 weeks gestation were obtained after therapeutic abortion, tissues were fixed, and immunocytochemistry was performed using monoclonal antibodies against purified rat or rabbit GH receptor. The specificity of staining was confirmed by preabsorption of the antibodies with 1) adult rat liver membranes or 2) human fetal liver membranes, both of which possess specific GH-binding sites, or 3) human fetal skeletal muscle membranes, which do not specifically bind GH. Positive staining was seen in a subpopulation of liver parenchymal cells, in the ductal and endocrine tissue of pancreas, in the germinal layer of the epidermis and the deeper dermal layers of skin, and in the tubular epithelium of kidney. No immunopositive staining was seen in skeletal or cardiac muscle, epiphyseal growth plate, lung, intestine, or adrenal. Positive staining was present in the neuronal cell bodies of the cerebral cortex. GH receptor was also detectable as early as 8 weeks gestation in syncytial layers of the placenta and was maintained until term. Results demonstrate the presence of immunoreactive GH receptor/binding protein in some human fetal tissues early in development. In particular, these results would support a role for GH in the growth and function of liver and pancreas.

Extraembryonic Membranes↗
PubMed1992

Demonstration and localization of growth hormone receptor in human skin and skin fibroblasts.

Clinical evidence suggests that skin is responsive to GH status in vivo. We sought to demonstrate the presence of GH receptors in human skin and in cultured skin fibroblasts using the techniques of immunohistochemistry and northern blotting. Human foreskin was obtained at surgery for preparation of sections and primary fibroblast cultures. Skin sections and fibroblast monolayers were immunostained using a monoclonal antibody which recognizes the hGH receptor (MAb 263). Positive immunoperoxidase staining was seen in all epidermal layers except the stratum corneum, in dermal sweat and sebaceous glands, and in dermal fibroblasts. In cultured fibroblasts capping of surface GH receptor was observed after aqueous formaldehyde fixation, whereas fixation in Carnoy's solution resulted in granular cytoplasmic staining. Fibroblast poly A+ RNA was prepared from cultured skin fibroblasts, separated by denaturing agarose gel electrophoresis, blotted onto nitrocellulose, and hybridized to a 32P-labeled, 847 base pair (bp) hGH receptor complementary DNA (cDNA) clone. Human liver and non-pregnant rabbit liver total RNA were used as controls. Fibroblast poly A+ RNA contained a single hybridizing species of approximately 5.2 kilobase. Human liver total RNA also contained a single hybridizing species of 4.9 kilobase. We have demonstrated the presence of GH receptor protein in human skin and growth hormone receptor mRNA and protein in cultured human skin fibroblasts. These observations suggest that GH may indeed have a direct role in modulating keratinocyte and fibroblast function.

Adolescent↗
PubMed1992

Prenatal expression of the growth hormone (GH) receptor/binding protein in the rat: a role for GH in embryonic and fetal development?

Although fetal growth is generally considered to be independent of pituitary growth hormone (GH), it is possible that pituitary GH plays a modulatory role in organ development or that a GH-like substance of non pituitary origin may influence fetal growth through the GH receptor. Accordingly, we have used immunohistochemistry, northern blot analysis, the reverse transcriptase-polymerase chain reaction and solution hybridization to study the ontogeny of the GH receptor/binding protein (BP) from the 12-day-old embryo (E12) to the E18 rat fetus. GH receptor/BP immunoreactivity was observed in all major organ systems of the E18 rat fetus and was not preferentially associated with any germ layer derivative. A general increase in GH receptor/BP immunoreactivity was evident from E12 to E18, with a marked increase occurring between E16 and E18. Hemangioblastic tissue was, however, strongly or intensely immunoreactive at all stages of development, as was the placenta. Most noteworthy of the other tissues expressing GH receptor/BP immunoreactivity by day 18 were skeletal and smooth muscle, chondroprogenitor cells, epithelial lining cells, neuronal ganglia, ependymal cells and the adrenal cortex. In the placenta, the most prominent immunoreactivity was associated with decidual cells. Total RNA was isolated from E12 to E18 rat fetuses and adult rat liver. Northern hybridization with a 35S-labelled rat GH receptor cRNA probe revealed that 3.9 kb and 1.2 kb transcripts complementary to the rat GH receptor riboprobe are present from at least E16. The existence of GH receptor mRNA at E12 and E14 was demonstrated by the polymerase chain reaction.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

The first disulphide loop of the rabbit growth hormone receptor is required for binding to the hormone.

Residues within the first disulphide loop of the GH receptor are highly conserved, and the two cysteines forming this motif are conserved across many cytokine receptors. We have used site-directed mutagenesis and the polymerase chain reaction with splicing by overlap extension to show that these residues are essential for binding of bovine (b)GH and human (h)GH to the rabbit GH receptor. When all residues within this loop were replaced with an equivalent polyalanine sequence, hormone binding was abolished. Conversion of Arg 39 within the loop to aspartate (R39D) decreased affinity for bGH by up to 20-fold. Conversion of Glu 42 to lysine (E42K) also resulted in a fivefold loss of affinity for bGH. However, charge reversals at Lys 37, Glu 44 and the conversion of Leu 43 to an arginine (as in the human receptor) were without a major effect on bGH binding. The lack of effect of the L43R mutation on bGH affinity, despite a significant (threefold) decrease in hGH affinity, argues against a role for Arg 43 as a residue conferring primate GH-binding specificity on the human receptor. Examination of the affinities of poly Ala, R39D and E42K mutants for a variety of hormone-binding-site directed and other monoclonal antibodies (MAbs) to the GH receptor revealed that these mutations were without a major effect on tertiary structure. It is of interest that the epitopes for the hormone-binding inhibitory MAbs 263 and 7 are located within this first loop, since the poly Ala mutation abolished the binding of both MAbs, and the R39D mutation abolished binding of MAb 7.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1991

The nuclear growth hormone receptor binding protein. Antigenic and physicochemical characterization.

The mechanisms involved in transcriptional regulation by growth hormone (GH) remain unknown. We report here that GH receptor immunoreactivity can be demonstrated in the nuclei of GH-responsive rat and rabbit tissues at both the light and electron micrograph level using monoclonal antibodies to the receptor extracellular domain. Nuclear staining is heterogeneous and associated with both chromatin and the nuclear membrane. To confirm these observations, nuclei were isolated from rabbit liver by two methods, one involving extensive nonionic detergent washes. Scatchard analysis of nuclear fractions revealed high affinity somatogenic receptor in nuclear membranes, nucleoplasm, and chromatin fractions. A panel of GH receptor monoclonal antibodies was used to further define these nuclear binding sites as being antigenically identical to microsomal receptor in all but one case. In addition, affinity cross-linking experiments showed the somatogenic binding subunit to have a reduced Mr of 67,000, similar to the Mr of the GH binding protein. We propose that the association of a GH binding protein with the nucleus may provide a means whereby GH can regulate the transcription of specific genes either directly or indirectly through nuclear kinase C activation. This speculation is congruent with the recent demonstration of a GH response element by Yoon et al. (Yoon, J. B., Berry, S. A., Seelig, S., and Towle, H. C. (1990) J. Biol. Chem. 265, 19947-19954).

Animals↗
PubMed1991

Growth hormone (GH) receptors in clonal osteoblast-like cells mediate a mitogenic response to GH.

GH receptors have not hitherto been demonstrated or characterized on osteoblasts. In this study we report the characterization of functional GH receptors on the clonal rat osteoblast-like cell line UMR 106.06. The receptors have a typical somatogenic specificity, with high affinity for human GH, 10-fold lower affinity for rat GH, and very poor affinity for rat PRL. The affinity for rat GH is 1.2 +/- 0.4 x 10(9) M-1, and there are approximately 9000 receptors per cell. GH binding increased over several hours when incubations were carried out in serum free minimal essential medium, but binding reduced rapidly when incubations were carried out in Tris-NaCl-Mg++, HEPES, or bicarbonate buffer, suggesting a critical dependence of receptor expression on nutritional factors. Rat GH stimulated proliferation of UMR 106.06 cells in a dose-dependent fashion with a maximum 43 +/- 2% stimulation above control and half-maximal effect at a final hormone concentration of 15 +/- 3 ng/ml. A proliferative response was not observed at low cell density, suggestive of a requirement for a threshold concentration of autocrine mediators or density-dependent receptor expression. A monoclonal antibody (MAb 263) which blocks GH binding to a subset (type 1) of rat hepatic GH receptors did not block binding to osteoblast GH receptors, and did not block the proliferative response. Thus, the proliferative response appears to be mediated by a class of GH receptors not blocked by MAb 263 and possibly related to the type 2 hepatic GH receptors. RNA was extracted from UMR 106.06 cells and a second osteoblast-like cell line UMR 201. Hybridization to a 32P-labeled complementary DNA probe to the rabbit hepatic growth hormone receptor revealed two major labelled bands (3.5 and 1.2 kilobases) and one minor band (2.4 kilobases) in both cell types. In summary, GH receptors are present in clonal osteoblast-like cells, and the receptors mediate a proliferative response to GH. The UMR 106.06 cells provide a valuable model system for studying the mechanism of GH action.

Animals↗
PubMed1991

Dual defects in pulsatile growth hormone secretion and clearance subserve the hyposomatotropism of obesity in man.

We have examined the mechanisms underlying reduced circulating GH concentrations in the obese human. Computer-assisted (deconvolution) analysis was used to determine endogenous GH secretory and clearance rates quantitatively from entire 24-h plasma GH concentration profiles. These analyses revealed that the half-life (t 1/2) of endogenous GH was significantly shorter in obese (11.7 +/- 1.6 min) than in normal weight subjects (15.5 +/- 0.81 min; P less than 0.01). The accelerated blood disposal rate of GH was not due to decreased circulating concentrations of GH-binding protein, since the latter were similar in obese (25 +/- 1.0%) and normal weight (24 +/- 2.3%) men. However, obese men had significantly fewer GH secretory bursts (3.2 +/- 0.53 vs. 9.7 +/- 0.67/day; P less than 0.01). Among the rare GH secretory bursts that occurred in obese subjects, there were significantly prolonged mean intersecretory burst intervals (282 +/- 65 vs. 131 +/- 11 min; P less than 0.05). The resultant daily GH production rate in obese men was reduced to one fourth that in normal weight individuals. Both GH secretion rate and burst frequency were negatively correlated with the degree of obesity (ponderal index). The decreases in GH burst frequency and half-life were specific, since GH secretory pulse amplitude (maximal rate of GH release), the mass of GH released per burst, and the duration of computer-resolved GH secretory bursts were not different in obese and normal weight men. We conclude that obese men harbor a double defect in GH dynamics involving both GH secretion and clearance, and that the severity of the GH secretory deficiency is proportionate to the degree of obesity.

Adult↗
PubMed1991

Epidermal growth factor (EGF) inhibits the secretomotor response of the thyroid: effects of EGF on radioiodine turnover and fluid transport in cultured porcine thyroid cells.

Thyrotrophin (4-256 microU/ml) promoted an increase in the rate of release of radioiodine from the organic iodine pool of cultured porcine thyroid cells in follicular formations. This action of TSH was antagonized by low concentrations of epidermal growth factor (EGF; 0.1-5 nmol/l). The maximal effect of EGF was reached by 0.5 nmol/l. EGF (0.5-5 nmol/l) also inhibited the stimulatory effect of 8-chloro cyclic AMP (0.06-1.0 nmol/l) on radioiodine turnover. Exposure of thyroid cultures to media with a calcium concentration of 17.7 mumol/l (1% of normal) resulted in a very marked increase in the rate of release of radioiodine. The effect of TSH in low-calcium media was to inhibit the increased release of radioiodine, and EGF (0.5 nmol/l) antagonized this inhibitory effect of TSH. The calcium ionophore, A23187, stimulated radioiodine release in a dose-dependent fashion, and EGF (1.7 nmol/l) inhibited this response. Fluid transport in thyroid monolayers was stimulated by prostaglandin E2 (PGE2; 1 mumol/l). EGF (5 nmol/l) also stimulated fluid transport, but antagonized the effect of PGE2 added subsequently. It was concluded that EGF exerted acute antagonistic effects on thyroid cell responses in vitro to cyclic AMP and agents promoting accumulation of cyclic AMP in time-frames too short for these inhibitory effects to be attributable to the dedifferentiative effect of the growth factor.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1990

Soluble forms of the rabbit adipose tissue and liver growth hormone receptors are antigenically identical, but the integral membrane forms differ.

Cytosolic, detergent-solubilized and membrane-bound growth hormone (GH) receptors from rabbit adipose tissue and liver were tested for reactivity with a panel of monoclonal antibodies (MAbs). The cytosolic and detergent-solubilized forms of adipose tissue and liver GH receptors were identically reactive with four precipitating and two hormone-binding-site-directed MAbs. However, the membrane-bound form of the adipose receptor was 1000-fold less reactive with one binding-site-directed MAb (MAb 7) than the membrane-bound liver GH receptor. Reactivity with another inhibitory MAb (MAb 263) was identical for adipose tissue and liver membrane GH receptors. The relative potency of 22,000-Mr and 20,000-Mr forms of human GH was identical in assays with liver and adipose tissue membrane receptors. Thus, contrary to earlier suggestions, the discrepancy between the growth-promoting and insulin-like activities of 20,000-Mr human GH cannot be rationalized by a difference in the affinity of this hormone for 'somatogenic' and 'metabolic' receptors when the comparison is made in the same species. Cross-linking studies showed that the major GH-binding subunit of liver and adipose tissue GH receptors had the same Mr (54,000 +/- 5000, reduced). The ligand-binding subunits of liver and adipose tissue receptors are identical by several criteria, but one epitope on the adipose tissue receptor appears to be masked upon membrane insertion, possibly by close association with a tissue-specific component. Tissue specificity may be determined by association of a ubiquitous GH-binding subunit with tissue-specific membrane components, rather than by differences in amino acid sequence.

Adipose Tissue↗
PubMed1990

Purification and partial sequence of the rabbit mammary gland prolactin receptor.

1. The prolactin receptor from rabbit mammary gland was purified to near homogeneity using a novel hydrophobic interaction chromatographic procedure. 2. Part sequencing (101 residues) revealed 34% identity with the rabbit liver growth hormone receptor, providing support for the existence of a new class of transmembrane receptors regulating growth and lactation.

Amino Acid Sequence↗
PubMed1990

An immunohistochemical assessment of cellular proliferation markers in head and neck squamous cell cancers.

Prognostic information is essential for the evaluation, judgement and optimal treatment of patients with squamous cell cancers (SCCs) of the upper aerodigestive tract. Using immunohistochemical and flow cytometric techniques, we have studied the significance of cellular expression of the Ki-67 antigen, epidermal growth factor receptor (EGFR), the transferrin receptor (TFR) and DNA ploidy status in a prospective analysis of patients with SCCs of the head and neck region. All 42 fresh tumour samples (five well differentiated; 28 moderately differentiated; nine poorly differentiated) expressed both EGFR and TFR to varying degrees. Receptor expression was most marked on the peripheral invading margin of cancer cell islands although staining was also demonstrated in a random fashion within cellular islands and consistently along the basal cell layer of overlying stratified squamous epithelium. The percentage of cancer cells that reacted with the Ki-67 monoclonal antibody was assessed as low (less than 10%) in 15 samples (35.8%), intermediate (10-30%) in 19 samples (45.2%) and high (greater than 30%) in eight samples (19.0%). Eleven of 15 samples (73%) with a low percentage reactivity were DNA diploid, whereas seven of eight samples (87.5%) with a high percentage reactivity were DNA aneuploid. Poorly differentiated SCCs were significantly more often aneuploid than were either moderately or well differentiated tumours. Our results suggest that EGFR and TFR are widely distributed on SCCs, especially on proliferating cells at the invading tumour margin. In addition, there is a close spatial correlation between cells expressing EGFR, TFR and those expressing the Ki-67 antigen. Tumours in which the staining intensity for both EGFR and TFR was intense invariably expressed the Ki-67 antigen in a high proportion of cells. Further patient follow-up will be important in determining whether intense EGFR and TFR staining, combined with a high percentage reactivity with Ki-67 antibody and DNA aneuploidy, will ultimately define a subset of head and neck cancer patients with a poor clinical outcome.

Aged↗
PubMed1990

Induction of responsiveness of rat diaphragm to ovine growth hormone after administration of reserpine.

The diaphragm of the pituitary intact rat is insensitive to the insulin-like effects of growth hormone unless weanling animals are used, and even then these effects are not achieved reliably. We report here that an intraperitoneal injection of reserpine is able to induce consistent responsiveness to ovine growth horomone (oGH) in hemidiaphragms from 20-27 day old rats as assessed by stimulation of 3H-AIB transport and 14C-phenylalanine incorporation into protein. Maximal stimulation of 3H-AIB transport (approximately 40%) can be elicited by addition of oGH (5 micrograms/ml) to hemidiaphragms after a 2 mg/kg injection of reserpine given 5 h prior to sacrifice. The degree of stimulation does not alter significantly if the rats are sacrificed 3, 5 or 12 h after administration of reserpine, although it decreases by 24 h. Administration of reserpine 3 h before sacrifice also leads to a 50% increase in 14C-phenylalanine incorporation into protein in rat diaphragms in response to the addition of oGH (5 micrograms/ml). The induced sensitivity to oGH is not due to inhibition of GH secretion by reserpine as demonstrated by RIA of plasma GH. Addition of a monoclonal antibody to the GH receptor (MAb263) did not result in a stimulation or inhibition of 3H-AIB uptake or stimulation of protein synthesis in reserpinized rat hemidiaphragms. These results suggest that reserpine can induce tissue responsiveness in rats 20-27 d.o. independent of plasma GH levels. Our results also imply that the type 1 GH receptor of Barnard, Bundesen, Rylatt and Waters (1985) does not mediate the insulin like actions of GH on rat diaphragm.

Aminoisobutyric Acids↗
PubMed1990

Growth hormone receptor expression in the rat gastrointestinal tract.

We have used immunohistochemistry to define the cellular distribution of GH receptors in the gastrointestinal tract (GIT) and its derivatives. Immunohistochemistry was performed in the adult rat GIT with a panel of characterized monoclonal antibodies to the GH receptor. The most intense and heterogeneous immunoreactivity was observed in epithelial cell subpopulations of GIT mucosa. Mesenchymal elements of the GIT were homogenously and moderately immunoreactive. Intense immunoreactivity was observed in the ductal epithelium of the sublingual gland, scattered basal epidermal cells of the esophageal mucosa, zymogen cells of the gastric glands, scattered surface epithelial cells of the stomach, and scattered peripheral pancreatic acinar groups. Scattered enteroendocrine cells and parietal cells, crypt and villous columnar cells of the small intestine, surface columnar cells of the cecum/colon, crypt base columnar cells of the colon, and contiguous peripheral cords of pancreatic islet cells displayed strong immunoreactivity. No immunoreactivity was detectable in the mucous and serous acini of the sublingual and submandibular gland, respectively, mucous-secreting cells of the base of the cardiac and pyloric glands, surface epithelial cells of the fundus, paneth cells, goblet cells of cecum/colon, or mucous cells at the base of the cecal crypt. Other elements of the GIT were moderately or weakly immunoreactive. In support of our localization we can detect high affinity binding (Ka = 3 x 10(9] of [125I]human GH with ovine GH as displacing ligand to crude homogenates of adult rat stomach and intestine. We conclude that discrete epithelial cell subpopulations of the GIT and its derivatives are directly responsive to GH action. GH may, therefore, act independently of or synergistically with hepatic insulin-like growth factor-I in executing its physiological and/or growth-promoting role in the GIT.

Animals↗
PubMed1990

Cellular localization of the growth hormone receptor/binding protein in the male and female reproductive systems.

We have used immunohistochemistry to localize GH receptor/binding protein (BP) in the male and female reproductive systems of adult rats. Testes and ovaries from neonatal animals were also examined to determine if GH receptor/BP expression in these tissues is developmentally regulated. Two monoclonal antibodies (MAb 43 and 263) were immunoreactive in identical locations whereas no immunoreactivity was evident when control monoclonal antibodies 7 and 50.8 were used. Localization of the receptor/BP was observed in both the nucleus and cytoplasm of immunopositive cells confirming our recent report of a nuclear GH receptor. Intense GH receptor/BP immunoreactivity in the male reproductive system was evident in the epithelium of the vas deferens and coagulating gland, the prostatic epithelium during the secretory phase, and the ductular epithelium of the coagulating and bulbourethral glands, respectively. Strong immunoreactivity was detectable in the Leydig and Sertoli cells, the epithelium of the ductus epididymis and seminal vesicles and smooth muscle of the tunica muscularis of the vas deferens, septae of the seminal vesicles, and in prostatic fibromuscular stroma. Cells of the seminiferous tubules (spermatogonia, primary and secondary spermatocytes, and spermatids) were moderately immunoreactive. No immunoreactivity was detectable in spermatozoa in the ductus epididymis or vas deferens, in scattered epithelial cells of the ductus epididymis, the prostatic epithelium in the nonsecretory phase, and mucous secreting cells of the bulbourethral glands. Leydig cells of 10-day postnatal rat testis were intensely immunoreactive whereas seminiferous tubular cells displayed homogenous immunoreactivity from moderate to strong. Intense GH receptor/BP immunoreactivity in the female reproductive system was evident in the germinal epithelium, the vascular endothelium of the myometrium, the epithelial lining of the fimbriae and oviduct, the endometrial epithelium and scattered endometrial glands, the mesothelium of the perimetrium, and the vascular endothelium of the endometrium. Strong immunoreactivity was exhibited by scattered oocytes, lutein cells of the corpus luteum, scattered endometrial glands, and the vascular endothelium of the endometrium. Moderate immunoreactivity was evident in scattered oocytes, granulosa cells, theca interna and externa, smooth muscle of the oviduct and myometrium, scattered endometrial glands, and luminally placed endometrial stroma cells. Ovarian granulosa cells from 10-day postnatal rats displayed strong immunoreactivity in contrast to moderate immunoreactivity in adult granulosa cells. In conclusion, we report a widespread distribution of the GH receptor/BP in the reproductive system of the rat by which GH may exert a direct action on reproductive function. The distribution is concordant with a role for GH in epithelial function and/or maintenance and also with a possible role for GH in the integrity of the endometrial vasculature.

Animals↗
PubMed1990

Regulation of growth hormone (GH) bioactivity by a recombinant human GH-binding protein.

The in vitro biological effects of serum GH-binding protein (GHBP) were measured in the mouse 3T3-F442A preadipocyte adipogenesis assay during GH stimulation. Coincubation of increasing concentrations of human (h) GH (0.14-4.5 nM) with 4.2 nM recombinant hGHBP-(1-247) in serum-free medium shifted the hGH dose-response curve to the right over the range 0.14-0.9 nM. When the hGH concentration was fixed at 0.45 nM, a dose-dependent inhibition of GH bioactivity was seen over the range of 0.1-11.3 nM GHBP, with an ED50 of 3 nM. The presence of serum had no effect on the inhibitory properties of GHBP. When 2% pooled human serum was added to incubation medium containing 0.45 nM hGH and GHBP (0.6 nM-5.7 nM), the effect of GHBP was again inhibitory, with an ED50 of 1.2 nM. Two percent serum alone was adipogenic, but at this low serum concentration it is likely that some factor other than GH is responsible. In a homologous receptor assay, the binding of [125I]hGH to IM-9 lymphocytes was inhibited in a dose-dependent manner by increasing concentrations of hGHBP in the physiological range, providing further support for the idea that GHBP can regulate the bioactivity of GH by blocking the binding of free GH to target tissues in vivo. Our results suggest that one function of GHBP is to dampen the biological effects of pulsatile GH secretion by reducing free GH during secretory pulses. This effect combined with an increased half-life of circulating GH would have the effect of flattening the hormone secretory profile at the target tissue level.

Adipose Tissue↗