Mammalian Growth Hormone Research Articles

Primary structure of elephant growth hormone†

The primary structure of elephant growth hormone was determined. The growth hormone was cleaved by proteolytic enzymes and cyanogen bromide. The resulting peptide fragments were separated by HPLC and then subjected to amino acid and sequence analyses. Elephant growth hormone consists of 190 amino acids with four cysteine residues. Sequence comparison with other mammalian growth hormones revealed that elephant growth hormone is highly homologous with that of pig and, to a much lesser extent, with that of human growth hormone.

Secondary structure prediction of 11 mammalian growth hormones.

The secondary structure of 11 mammalian growth hormones has been predicted by combining five different methods. Three long helical regions located around residues 20, 120, and 170 constitute the most prominent common feature in the species studied. The strong amphiphilic character of these helices suggests that they can play an important role in protein folding or stability.

Structure of a fish (rainbow trout) growth hormone gene and its evolutionary implications.

We have isolated and sequenced a clone from a rainbow trout (Salmo gairdneri) genomic library that carries a gene encoding a fish growth hormone (GH). This gene spans a region of approximately equal to 4 kilobases, nearly twice that of mammalian GH genes. The trout GH gene is comprised of six exons, in contrast with five exons in mammals. The additional intron in the fish gene interrupts translated regions that are analogous to the last exon of its mammalian counterpart. In addition, the alleged internally repeating sequence in mammalian GH, prolactin (Prl), or placental lactogen (PL) is not observed in the predicted polypeptide sequence of fish GH. Direct repeats that flank exons I, III, and V of the mammalian GH, Prl, and PL genes are absent in the fish GH gene. These findings indicate that the rainbow trout GH gene structure does not support the current hypothesis that internally repeated regions in GH, Prl, and PL arose from a small primordial gene.

Plerocercoid growth factor: a Homologue of human growth hormone

Plerocercoids of the tapeworm, Spirometra mansonoides, produce a factor with characteristics similar to those of mammalian growth hormone (GH). Plerocercoid growth factor (PGF) stimulates growth and mimics other actions of GH but does not possess the anti-insulin/diabetogenic activities intrinsic to mammalian growth hormones. Duplication of activities unique to human GH, chemical and physical similarities, plus crossreactivity with strictly specific anti-hGH monoclonal antibodies, underlie the hypothesis that S. mansonoides has obtained and expresses a human gene for GH. In this article, Kirk Phares discusses the similarities between the two hormones.

Similarities and Differences Among Prolactins and Growth Hormones and Their Receptors

SYNOPSIS. Data from the literature and from our own studies on the receptors for prolactin (PRL) and growth hormone (GH) are reviewed and analyzed. Receptors for PRL have been studied in a wider range of species and in a greater diversity of target organs than have the binding sites for GH. Although GHs are structurally more highly conserved among the vertebrates than are PRLs, the available data indicate that there is greater diversity among GH receptors than there is among PRL receptors. In general, GH receptors show greater species specificity but less hormone specificity than do PRL receptors. The reason for the greater diversity among GH receptors as compared to PRL receptors is unknown; it bears no relationship to phylogeny. Data on the binding of purified preparations of mammalian PRL, GH and placental lactogen (PL) to renal and hepatic receptors for PRL and GH, respectively, of several vertebrate species are reviewed. The species and hormone specificity of the binding of the hormones to the two typesof receptors showed no consistent pattern. To explain this disarray, we propose that the receptor binding domains of PRL and GH were present in their common ancestral gene and that they havebeen retained to variable degrees by all of the descendant members of the PRL-GH family. We further propose that hormone and species specificity of binding is determined by hindering features on the hormones and on the receptors, rather than by merely the presence or absence of the appropriate binding determinants.

Sequence of the notch locus of Drosophila melanogaster: relationship of the encoded protein to mammalian clotting and growth factors.

The Notch locus is essential for proper differentiation of the ectoderm in Drosophila melanogaster. Notch corresponds to a 37-kilobase transcription unit that codes for a major 10.4-kilobase polyadenylated RNA. The DNA sequence of this transcription unit is presented, except for portions of the two largest intervening sequences. DNA sequences also were obtained from three Notch cDNA clones, allowing the 5' and 3' ends of the gene to be mapped, and the structures and locations of nine RNA coding regions to be determined. The major Notch transcript encodes a protein of 2,703 amino acids. The protein is probably associated with cell surfaces and carries an extracellular domain composed of 36 cysteine-rich repeating units, each of about 38 amino acids. The gene appears to have evolved by repeated tandem duplications of the DNA coding for the 38-amino-acid-long protein segments, followed by insertion of intervening sequences. These repeating protein segments are quite homologous to portions of mammalian clotting factors IX and X and to the product of the Caenorhabditis elegans developmental gene lin-12. They are also similar to mammalian growth hormones, typified by epidermal growth factor.

Some Biochemical Effects of the Growth Hormone Analogue Produced by Plerocercoids of the Tapeworm Spirometra mansonoides on Carbohydrate Metabolism of Adipose Tissue from Normal, Diabetic, and Hypophysectomized Rats

Plerocercoids of Spirometra mansonoides produce a functional analogue of mammalian growth hormone (GH). Plerocercoid growth factor (PGF) mimics the growth-promoting actions of GH, but has not been shown to duplicate all of the actions reported for GH. The purpose of this study was to determine the effects of plerocercoid infection (chronic PGF treatment) on glucose metabolism of adipose tissue and to compare the effects to those elicited by insulin and GH in intact, diabetic, and hypophysectomized male rats. Groups of rats were constantly exposed to PGF (via plerocercoid infection) or injected twice daily with bovine GH, insulin, or saline for 10 days. Basal oxidation rates of [U-14C]glucose to 14CO2 in adipose tissue segments were measured in vitro immediately after tissue removal. Other aliquots of adipose tissue were preincubated in hormone-free medium for 3 hr prior to testing the ability of the tissue to respond to insulin or human GH (hGH) added in vitro. Adipose tissue from PGF-treated intact and hypophysectomized rats had significantly elevated basal glucose oxidation rates, and the tissue was sensitive to further stimulation by insulin or hGH. The results obtained with intact and hypophysectomized rats were essentially the same, indicating that the effects of PGF were not due to suppression of endogenous GH. The basal glucose oxidation rate in adipose tissue from diabetic rats was stimulated (P less than 0.01) by PGF, but the tissue was not sensitive to insulin added in vitro. Furthermore, PGF had no effect on body growth or blood glucose concentrations of diabetic rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Rainbow Trout (Salmo gairdneri) Growth Hormone: in vitro Translation of Pituitary RNA and Product Analysis

We have used RNA blot analysis, in vitro translation, and protein immunoblot analysis to characterize mRNA in the pituitary glands of rapidly growing rainbow trout (Salmo gairdneri). Cell-free translation products of total RNA, analyzed by direct immunoprecipitation or western immunoblot analysis with an antiserum to chum salmon (Oncorphynchus keta) growth hormone (GH), indicate that rainbow trout pregrowth hormone (pre-GH) is a polypeptide of 25 000 Da. RNA blot analysis of total pituitary RNA to its cDNA, using total liver RNA as a competitor, revealed the presence of at least four size classes of pituitary mRNA sequences. One class, with a size smaller than 18S rRNA, is the predominant mRNA component. By in vitro translation and western immunoblot analysis, the pre-GH mRNA activity is associated with this class of mRNA sequences. These results suggest that rainbow trout pre-GH mRNA is in the same size range as that of mammalian GH mRNA.

Effect of mammalian growth hormone and prolactin on the growth of hypophysectomized chickens.

Body weight gain and shank-toe growth during a 26-day treatment period following hypophysectomy were 55 and 46%, respectively, of control values, but the body weight gain was unaffected and bone growth only slightly reduced when the hypophysectomized chickens were fed a low dose of corticosterone (5 ppm). Bovine growth hormone (0.5 mg GH/kg body wt/day for 18 days) enhanced body weight gain and shank-toe length increase (an estimate of bone growth) by 46 and 33%, respectively, compared to the growth of hypophysectomized chickens receiving only corticosterone. These same endpoints were increased approximately 24% after ovine growth hormone treatment in hypophysectomized chickens not receiving corticosterone. Body weight gain during 18 days of treatment with bovine prolactin (0.5 mg PRL/kg/day) was 27% greater than the value for corticosterone-treated hypophysectomized chickens, but bone growth was unaffected. The mammalian GH preparations increased heart weight of the hypophysectomized chickens (25-29%), but pectoralis muscle weight was unaffected. GH treatment enhanced thymal weights by 71% in corticosterone-treated hypophysectomized chickens, and by 93% in hypophysectomized animals not receiving corticosterone. GH had no significant effect on bursal weights, and PRL had no effect on either of these lymphoid organ weights in corticosterone-treated hypophysectomized chickens. GH increased liver and adipose tissue weights considerably more than the large increases that followed treatment of hypophysectomized chickens with corticosterone alone (69 and 126% greater, respectively), but had no effect on these endpoints in hypophysectomized chickens not receiving corticosterone. PRL also greatly increased liver and adipose tissue weights in corticosterone-treated hypophysectomized chickens (79 and 75%, respectively). These results provide evidence that mammalian GH enhances body weight gain, bone growth, and the growth of several organs in the hypophysectomized chicken. Mammalian PRL increased body weight gain, liver weight, and adipose tissue weight in corticosterone-treated hypophysectomized chickens, but did not influence bone growth or the weights of the heart, pectoralis, thymi, or bursa.

Development and validation of a salmon growth hormone radioimmunoassay

A highly specific and sensitive radioimmunoassay (RIA) for the measurement of plasma and pituitary growth hormone (GH) levels in salmonid fishes was developed using an antiserum raised in rabbit against chum salmon ( Oncorhynchus keta) GH (sGH). Pituitary extracts and plasma from chum, coho, masu, and amago salmon, and from rainbow trout and Japanese charr, all exhibited displacement curves parallel to the sGH standard. Samples from the eel, carp, goldfish, and tilapia, as well as plasma from hypophysectomized chum salmon and rainbow trout, all showed negligible cross-reactivity. None of the mammalian or teleostean GH or prolactin preparations tested cross-reacted with the antibody in the assay system. RIA sensitivity was 0.6 ng sGH/ml of plasma when 100 μl of plasma was employed. Intra- and interassay coefficients of variation were 3.9 and 4.1%, respectively. Plasma GH levels of the mature chum salmon caught in Otsuchi Bay were highly variable, especially in females (20.2 ± 8.2 ng/ml) as compared with males (16.0 ± 1.1 ng/ml), and there was no significant change after transfer to fresh water. Whereas there was no change in plasma GH levels in males kept in seawater, the levels in females increased with time in close correlation with the increase in plasma chloride.

Nucleotide sequence of mouse prolactin and growth hormone mRNAs and expression of these mRNAs during pregnancy.

The mRNAs for mouse prolactin and growth hormone have been isolated from anterior pituitary glands and cloned as cDNAs. The nucleotide sequences of these mRNAs have been determined, and these sequences, along with the predicted amino acid sequences, are compared to those of other mammalian prolactin and growth hormone mRNAs. Levels of prolactin and growth hormone mRNAs during pregnancy have been monitored by hybridization to the cloned cDNA probes. We find the levels of these mRNAs to remain nearly constant during mid-to-late gestation.

Development and validation of a salmon prolactin radioimmunoassay

A highly specific radioimmunoassay (RIA) for the measurement of prolactin (PRL) in the plasma and pituitary of salmonid fishes was developed using a rabbit antiserum to chinook salmon ( Oncorhynchus tschawytscha) PRL. The PRLs purified from chinook salmon and chum salmon ( O. keta) pituitaries showed exactly the same competitive inhibition curves in the RIA, regardless of iodination of either hormone. The displacement curves for pituitary extracts and plasma from several salmonids, including chum, coho, and amago salmon, rainbow trout, and Japanese charr, were parallel to the salmon PRL standard, whereas those from the eel, goldfish, carp, and tilapia showed negligible cross-reactivity. Negligible cross-reactivity was also seen with plasma from hypophysectomized rainbow trout or coho salmon. None of the mammalian PRL or growth hormone (GH) preparations, bullfrog PRL, or presumptive chum salmon “gonadotropin” and eel “PRL” cross-reacted in the PRL RIA. Presumptive chum salmon GH showed less than 0.05% cross-reactivity. The RIA sensitivity was less than 0.1 ng of the salmon PRL standard per milliliter. The immunoreactive reactive plasma PRL levels in mature chum salmon were below 1 ng/ml in seawater. The plasma PRL in females increased to about 8 ng/ml 1 day after transfer to fresh water, and high levels (2–4 ng/ml) were maintained during 3–7 days after the transfer. In contrast, when males were transferred to fresh water, an increase in plasma PRL was seen only 1 day after the transfer. A significant decrease in plasma osmolality was observed in both males and females after transfer to fresh water. No change was observed either in plasma PRL or osmolality, when fish were transferred from seawater to seawater.

Effect of mammalian growth hormone on amino nitrogen mobilization in the eel

Hypophysectomy decreased plasma amino nitrogen (PAN) levels of Japanese eels. In contrast, administration of bovine or ovine growth hormone (GH; 2 μg/g) produced a delayed increase in PAN levels of both intact and hypophysectomized eels 48 hr after GH injection. The minimum dose of GH required to elevate PAN levels was found to be 0.1–1 μg/g body wt. The fact that GH treatment also increased PAN of hepatectomized eels indicates that the increased PAN was at least partly caused by the increased mobilization of amino nitrogen from body protein. GH also increased plasma free fatty acid content of intact and hypophysectomized eels 48 hr after GH injection in one experiment of the present study, but this effect was not reproducible in other experiments. No effect of GH administration was observed either in plasma glucose and lipid of intact and hypophysectomized eels 48 hr after the injection.

Effects of hypophysectomy and substitution with growth hormone, prolactin, and thyroxine on growth and deposition in juvenile frogs, Xenopus laevis

Growth was studied in young metamorphosed frogs, Xenopus laevis, following hypophysectomy and substitution with mammalian growth hormone (bGH or pGH), mammalian prolactin (oPRL), and thyroxine. Hypophysectomy reduced growth (weight and length increase). GH and PRL proved equally efficient in restoring growth and in mobilizing energy stores (fat bodies and liver glycogen). No synergistic effects between GH and PRL could be observed. GH exerted its growth-promoting effects by increasing gross food conversion efficiency (weight increase/food intake), but did not stimulate appetite. Moderate GH doses given to a group of frogs in growth stagnation exerted moderate metabolic effects, and may have stimulated appetite in some animals, but did not increase body size significantly. Thyroxine was unable to promote growth, but increased mobilization of energy stores. Hypophysectomy and hormone substitution affected feeding behavior. The nature of the actions of pituitary somatotropic hormones and of thyroxine on growth and deposition is discussed.

Sexual differences in the in vitro induction of vitellogenesis in the turtle: Role of the pituitary and growth hormone

1. 1. Estradiol induces vitellogenin synthesis in liver cultures taken from normal and ovariectomized female turtles. 2. 2. By contrast, estradiol alone or with other hormonal or serum factors failed to induce vitellogenin synthesis in liver cultures established from normal and castrated males. 3. 3. In vitro induction of vitellogenesis was achieved only in cultures originated from hypophysectomized males and in the presence of both estradiol and mammalian growth hormone. 4. 4. These results demonstrated a clear sex difference in the hormonal stimuli required, in vitro, for the induction of vitellogenesis in the turtle. 5. 5. We suggest that pituitary growth hormone is an important synergist in the vitellogenic response to estrogen, possibly through an effect on estrogen receptors.

Effect of hypophysectomy on estrogen-induced vitellogenin synthesis in the green frogRana esculentacomplex

Abstract The control mechanism of vitellogenin synthesis and/or release by the liver has been investigated in the green frog, Rana esculenta. The effects of estradiol on vitellogenin serum titres have been evaluated in adult females after hypophysectomy and/or ovariectomy and treatment with Cortisol, growth hormone (GH), and homologous pituitary suspensions. The results indicated that the estradiol-dependent vitellogenin synthesis and/or release needs a hypophysial principle (s) to be fully stimulated. Attempts to identify this substance (s) showed that it is different from Cortisol and mammalian GH.

Purification and properties of chicken growth hormone and the development of a homologous radioimmunoassay

Highly purified growth hormone (GH) has been isolated from pituitary glands of chicken ( Gallus domesticus), and a specific homologous radioimmunoassay (RIA) has also been developed. The purified chicken GH was active in the rat tibia bioassay and it gave a dose-dependent response which paralleled that of the bovine GH standard. High pressure liquid chromatography revealed that the purified chicken GH was homogenous. Chicken GH had an R f value of 0.2 in disc electrophoresis, and a MW of 26,000 from sodium dodecyl sulfate-gel electrophoresis. The isoelectric point was estimated to be 7.6 by gel isoelectric focusing. The amino acid composition of chicken GH was found to be similar to that of mammalian GH, and the NH 2-terminal amino acid was threonine. Partial sequencing (114 amino acids) of the chicken GH showed 79% homology with bovine GH. An antiserum was developed to the purified chicken GH in a rabbit, and it was used to develop a homologous RIA using 125I-labeled chicken GH as the ligand. The purified chicken GH was iodinated via the lactoperoxidase method to a specific activity of approximately 100 μCi/μg. Plasma from chickens, medium from incubation of pituitary glands, and homogenates of pituitary glands gave parallel dilution-response curves with the chicken GH standard. Mammalian GH, prolactin (PRL), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) showed no cross-reaction with the 125I-labeled chicken GH. Purified turkey GH showed parallel dose response with the chicken GH, but purified turkey PRL did not cross-react. Chicken FSH and LH also showed no inhibition of binding. The minimum detectable concentration of the assay was 0.93 ng/tube, and the intraassay and interassay coefficients of variation were 9 and 16%, respectively. The specific binding of 125I-labeled chicken GH to a microsomal fraction isolated from chicken liver was identified, and the specific binding was generally low (1–4%). Turkey PRL, and chicken LH and FSH showed no inhibition of the 125I-labeled chicken GH hepatic binding and the ontogeny of the hepatic GH receptor binding sites in male and female chickens was examined.

Application of recombinant DNA technologies to studies on chicken growth hormone.

Messenger RNA isolated from chicken pituitaries was used to construct a chicken pituitary cDNA library. A chicken growth hormone cDNA clone was isolated using 32P-labeled mammalian growth hormone cDNA probes. The amino acid sequence (derived from the DNA sequence) of the mature form of chicken growth hormone shows 77% homology with that of bovine growth hormone. The chicken growth hormone cDNA clone was used to generate a vector capable of producing chicken growth hormone in Escherichia coli. The recombinant E. coli-derived chicken growth hormone was similar to pituitary chicken growth hormone in several biochemical and immunological properties. The recombinant-derived hormone has been used to establish a sensitive radioimmunoassay for growth hormone determinations made from chicken sera. The chicken growth hormone gene has also been introduced into a retroviral vector capable of establishing productive infections of chicken cells both in in vitro and in vivo. The resulting infections are accompanied by the production of radioimmunoassay-detectable growth hormone. The concentrations of growth hormone in sera of Leghorn chickens infected with the recombinant retrovirus are three- to tenfold higher than in control animals.

Development and characterization of a homologous radioimmunoassay for equine prolactin.

A specific and sensitive homologous radioimmunoassay has been developed for equine prolactin, suitable for measuring prolactin concentrations in serum of horses. The sensitivity of the assay ranged from 0.4 to 0.6 ng/ml and the intra- and inter-assay coefficients of variation averaged 6.9 and 15.4%, respectively, for five doses of hormone. Cross-reactivity with other mammalian and nonmammalian prolactins and growth hormones was less than 20 and 0.3%, respectively. Cross-reactivity with equine growth hormone was less than 0.07%. Equine serum and pituitary extracts showed parallel dilution-response curves with equine prolactin. The percentage recovery of exogenous equine prolactin in serum was 89%. Preliminary analysis of several physiological samples (stallions, pregnant, and nonpregnant mares) yielded values from 0.6 to 12.0 ng/ml.

Biological and binding activities of pituitary hormones from the ostrich, Struthio camelus

Biological and binding activities of adenohypophysial hormones purified from the ostrich (ost), Struthio camelus, were compared to those of the corresponding hormones derived from mammalian and other avian species. The potency of ostrich prolactin was comparable to those of other avian preparations and slightly less active than the ovine hormone when tested in the pigeon crop-sac assay, but ostrich growth hormone (GH) was more potent than several other avian preparations and was comparable to mammalian GH in the rat tibia bioassays. Marked discrepancies were evident in the activities of both ostrich gonadotropins (ostGn) when they were tested in a variety of in vivo and in vitro bioassays and radioreceptor assays (RRAs). Both the ostrich follicle-stimulating hormone (ostFSH) and luteinizing hormone (ostLH) were among the most potent tested thus far in in vivo bioassays for total gonadotropin in a lizard and a cockerel; a high sialic acid content may account for these high potencies. OstFSH was also the most potent nonmammalian Gn tested in two FSH specific mammalian bioassays, an in vivo (ovarian augmentation) and an in vitro (cAMP production) rat bioassay; in fact, ostFSH behaved more like a mammalian than an avian hormone in these assays. However, the binding activity of ostFSH was not unlike that of other avian FSH preparations when tested in either mammalian or nonmammalian FSH-RRA systems. OstLH was more potent than other avian preparations in an in vitro mammalian bioassay, but not in avian or amphibian LH bioassays; species specificity was pronounced among these LH assays. Binding activities of ostLH in mammalian and avian LH-RRAs were generally consistent with potencies in the two species of bioassays. However, a marked discrepancy was apparent in the behavior of ostLH in FSH-RRAs. Although ostLH had very low FSH activity when tested by radioimmunoassay, by bioassay, or by FSH-RRA with avian gonads, it was equipotent to ostFSH in competing for FSH-binding sites on the mammalian gonad; in this respect it was more like turkey than chicken LH. The ability of ostLH to antagonize the biological activities of ostFSH in the stimulation of cAMP by rat seminiferous tubules confirms that ostLH binds to the same functional receptors as FSH on the rat testis, even though it does not induce the characteristic physiological response associated with FSH.