Conformational comparison of human pituitary growth hormone and human chorionic somatomammotropin (human placental lactogen) by second-order absorption spectroscopy

Second-order absorption spectra strongly suggest the presence of a hydrogen bond between the single Trp of human pituitary growth hormone (hGH) and a carboxylate ion. This hydrogen-bonded complex is buried within the hydrophobic interior of the hGH molecule. Although the homologous Trp in human chorionic somatomammotropin [human placental lactogen, HCS(hPL)] is also buried within the hydrophobic interior of the molecule, there is no evidence that it is hydrogen bonded in the native protein. However, during the early stages of thermolysin digestion of HCS(hPL), both difference and second-order absorption spectra do indicate the transient presence of a similar hydrogen-bonded Trp-carboxylate complex. The molar extinction coefficients of hGH and HCS(hPL) have been refined.

beta-Endorphin: evidence for the existence of opioid and non-opioid binding components for the tritiated human hormone in NG108-15 cells

Human beta-endorphin (beta h-EP) binding on neuroblastoma X glioma hybrid NG108-15 cells using tritiated human beta endorphin (3H-beta h-EP) as a primary ligand was found to have a component which was not displacable with [D-Ser2 )-Leu-enkephalin-Thr6 (DSLET). The beta h-EP binding on these cells after saturation of the delta opiate sites with 200 nM DSLET was further characterized with synthetic beta h-EP analogs. The nonopioid binding site appears to recognize beta h-EP-(6-31), beta h-EP-(21-31) and beta h-EP-(28-31). Under these conditions, these COOH-terminal segments fully displace the tritiated beta h-EP. However, beta h-EP-(1-27) does not further displace 3H-beta h-EP in the presence of DSLET. The fact that a combination of DSLET and beta h-EP-(6-31) results in a full displacement of 3H-beta h-EP provides direct evidence for the existence of two binding sites for beta h-EP in NG108-15 cells, one recognizing the NH2-terminal enkephalin sequence and the other the non-opioid COOH-terminal segment.

Structural requirements and species specificity of the inhibition by beta-endorphin of heavy acetylcholinesterase from vertebrate skeletal muscle

The molecular forms of acetylcholinesterase in extracts of gastrocnemius muscle from four vertebrate species and in electric eel (Electrophorus) electric organ were separated and identified by low-salt precipitation and velocity sedimentation. The activity of the heavy insoluble (A12) form of human muscle acetylcholinesterase was inhibited by synthetic human beta-endorphin (500 mM). The homologous form in rat muscle extracts was poorly inhibited by human beta-endorphin at the same concentration, but was more effectively inhibited by camel beta-endorphin. The activities of heavy forms of pseudocholinesterase, present in small amounts in both species, were not reduced by beta-endorphin. Selective inhibition of homologous heavy forms of acetylcholinesterase activity by camel and human beta-endorphin was also seen in skeletal muscle extracts from frog and pigeon, but with decreased effectiveness. No inhibition was detectable in the heavy acetylcholinesterase form from extracts of electric organ tissue of the electric eel. The inhibition of heavy acetylcholinesterase activity in human muscle by human beta-endorphin was dependent on the presence of its NH2-terminal pentapeptide sequence. Maximal inhibitory potency depended on the presence of the entire amino acid sequence, since potency was considerably reduced in synthetic peptide analogues lacking either middle or COOH-terminal segments of beta-endorphin. The relative potency of beta-endorphin from various species as inhibitors of rat heavy acetylcholinesterase activity was also investigated. beta-Endorphin sequences most closely resembling that of the rat peptide (camel, equine) were most potent, whereas those with sequence differences of more than one amino-acid were less potent (turkey, human) or had no inhibitory activity (ostrich). The selective inhibition of heavy acetylcholinesterase by beta-endorphin thus exhibits species specificity, even among mammals, in which homologues of this molecular form of the enzyme are otherwise indistinguishable.

Beta-endorphin: demonstration of binding sites in three human neuroblastoma cell lines specific for the COOH-terminal segment of the human hormone

This communication reports for the first time specific binding sites in human neuroblastoma cells for human beta-endorphin (beta h-EP). Three cell lines (IMR-32, NMB and Kelly) were investigated and found to bind tritiated beta h-EP with an apparent dissociation constant of 2.2-4.2 nM. Further characterization with camel beta-EP and synthetic analogs indicated that the binding is most likely mediated by the COOH-terminal segments. beta h-EP-(6-31) had significant potency (15-75%) and beta h-EP-(1-27) was without displacing activity. The camel beta-EP has below 1% of the human beta-EP activity.

beta-Endorphin-induced analgesia is inhibited by synthetic analogs of beta-endorphin

Competitive antagonism of human beta-endorphin (beta h-EP)-induced analgesia by synthetic beta h-EP analogs with high in vitro opiate receptor binding to in vivo analgesic potency ratio has been demonstrated. A parallel shift of the dose-response curve for analgesia to the right was observed when either beta h-EP or [ Trp27 ] -beta h-EP was coinjected with various doses of [Gln8, Gly31 ]-beta h-EP-Gly-Gly-NH2, [Arg9,19,24,28,29]-beta h-EP, or [ Cys11 ,26, Phe27 , Gly31 ]-beta h-EP. It was estimated that the most potent antagonist, [Gln8, Gly31 ]-beta h-EP-Gly-NH2, is at least 200 times more potent than naloxone.

beta-Endorphin: characterization of binding sites specific for the human hormone in human glioblastoma SF126 cells

The established human glioblastoma cell line SF126 was found to bind tritiated human beta-endorphin (beta h-EP) in a saturable fashion. From displacement studies, the ED50 was estimated to be about 2.5 nM. The Kd was estimated as 1.9 X 10(-9) M and Scatchard analysis showed a biphasic pattern with a predominant low-affinity component. Binding reached a maximum at about 90 min at 22 degrees C and was instantaneously reversible. Tritiated [D-Ala2,D-Leu5]enkephalin and tritiated dihydromorphine did not bind to the cells. Sodium at a concentration of 150 mM decreased the specific binding by 80%. The interaction with the cellular binding site appeared to be mediated by the COOH-terminal segment of beta h-EP, as beta h-EP-(6-31) retained a high potency for displacing tritiated beta h-EP, and beta h-EP-(1-27) has no activity. Camel beta-EP was only about 1% as active as the human hormone.

Effects of beta-endorphin fragment 6-31 on morphine- and beta-endorphin-induced growth hormone and prolactin release

A fragment of human beta-endorphin (beta h-EP-(6-31] has been proposed as an endogenous inhibitor of beta-endorphin. We have evaluated the effects of the fragment on beta-endorphin- and morphine-induced prolactin and growth hormone release. It inhibited both morphine- and beta-endorphin-induced prolactin release, while it was ineffective on the release of growth hormone.

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.

Isolation, structure, and synthesis of a human seminal plasma peptide with inhibin-like activity

A basic peptide isolated from pooled human seminal plasma exhibited inhibin-like activity by suppressing pituitary follicle-stimulating hormone secretion in vitro and in vivo. The peptide has been characterized and sequenced, and a 31-amino-acid synthetic replicate showed full biological activity in vitro.

beta-endorphin-(1-27) is an antagonist of beta-endorphin analgesia

beta h-Endorphin-(1-27), a naturally occurring fragment of human beta-endorphin (beta h-endorphin), diminishes the analgesic effect of beta h-endorphin when coinjected intra-cerebroventricularly into mice. A parallel shift in the dose-response curve of beta h-endorphin in the presence of beta h-endorphin-(1-27) suggests competition at the same site. The potency of beta h-endorphin-(1-27) in antagonizing analgesia is greater than 4 times greater than that of the opiate antagonist naloxone.

Detection of bovine pancreatic trypsin inhibitor (bPTI) in bovine and ovine pituitaries, bovine brain, and adrenal medulla. A specific radioimmunoassay for bPTI

An antiserum against bovine pancreatic trypsin inhibitor (bPTI) has been raised in rabbits. The antiserum does not cross-react with known pituitary hormones and other proteins. A specific radioimmunoassay for bPTI has been developed. The ED50 is about 250 fmol per assay tube and the sensitivity is reliable to 15 fmol per tube. Immunoreactivity could be detected in bovine and sheep pituitaries, bovine brain, and adrenal medulla, but not in human, pig, and rat pituitaries. In the bovine pituitary the immunoreactivity is restricted to the posterior lobe.

Two cases of hereditary diabetes insipidus, with an autopsy finding in one

Two cases of hereditary diabetes insipidus (DI) are described, with an autopsy finding in one. The patients were brothers and 7 other relatives had symptoms of DI. The transmission of the disease in this family seemed to be an autosomal dominant trait with incomplete penetration. Both patients had the incomplete type of DI, which is diagnosed by the response of plasma AVP and the change in Uosm/Posm to 14 h water deprivation. The post-mortem examination in Case 1 showed that there was no atrophy of the supraoptic nucleus and paraventricular nucleus, but immunohistochemical studies revealed, that the paraventricular nucleus scarcely had any vasopressin positive cells in contrast to an autopsy control. This finding suggests that there may be a congenital defect in AVP synthesis in some cases of hereditary DI.

The response of plasma arginine vasopressin to 14 h water deprivation in the elderly

The response of plasma arginine vasopressin (AVP) to 14 h water deprivation was investigated in 30 healthy elderly individuals ranging in age from 63 to 87 years, with a mean age of 76.5 years. The mean AVP concentrations, both at normal hydration and after the water deprivation test, were significantly lower than those in the young. Moreover, the post-test mean value of Uosm/Posm in the elderly increased up to 1.55 +/- 0.52, which is lower than that in the young in whom the value was greater than 2. These results suggest that the aged are prone to incomplete diabetes insipidus. This pathological state might predispose to electrolyte imbalance in the elderly.

Synthetic somatomedin C: comparison with natural hormone isolated from human plasma

The biological and immunological properties of a chemically synthesized preparation of somatomedin C (Sm-C) were compared with those of the natural product isolated from human plasma. The two preparations produced identical curves in the radioimmunoassay and radioreceptor assay for Sm-C and in the radioreceptor assay for insulin. They were identical in their ability to stimulate DNA synthesis in confluent BALB/c 3T3 cells previously exposed to platelet-derived growth factor, and the biological activities of both preparations were completely neutralized by a monoclonal antibody raised against native Sm-C. These studies demonstrate that the chemically synthesized product is equivalent to the native molecule in all important respects and that it can be used interchangeably with the natural product for any studies that are contemplated.

Adrenocorticotropin. 57. Synthesis and biological activity of ostrich and turkey hormones

Synthesis of ostrich and turkey corticotropin (ACTH) has been accomplished by the solid-phase method. Each was identical to the natural hormone in high performance liquid chromatography. Relative potencies in a lipolytic assay in isolated rabbit fat cells were: human ACTH, 100; ostrich ACTH, 53; turkey ACTH, 28. In isolated rat fat cells relative lipolytic potencies were: human ACTH, 100; ostrich ACTH, 2; turkey ACTH, 13. It was concluded that lipolytic potency is sensitive to alterations in structure throughout the entire length of the ACTH sequence in the rat fat cell assay.

Synthesis of shrimp red pigment-concentrating hormone analogs and their biological activity in locusts

Two analogs of the red pigment-concentrating hormone (RPCH) have been synthesized by the solid-phase method: [Thr6]-RPCH (I) and [Tyr4, Thr6]-RCPH (II). Analog I has the same amino acid composition as the second adipokinetic hormone (AKH-II) isolated from locust corpora cardiaca. Bioassay for lipid-mobilizing activity in adult male locusts gave the following increases in hemolymph lipid content: AKH-I, 3.5; I, 2.4; II, 2.9. The biological response shown by I lends support to the conclusion that its sequence is that of the presumptive AKH-II. Replacement of Phe in position 4 by Tyr does not reduce the adipokinetic response.

Studies on prolactin: conformational comparison of human, equine, and porcine pituitary prolactins

The conformations of human, equine, and porcine pituitary prolactins, as evidenced by various optical properties, have been compared. The alpha-helix contents of all three proteins are essentially identical to each other (60 +/- 5%), as well as to prolactins isolated from other mammalian species. Direct absorption (zero and second-order), difference absorption, fluorescence emission, and circular dichroism spectra suggest that the majority of tyrosine and tryptophan side chains in these three proteins exist in very similar microenvironments within the folded forms of the hormones. Thus, the general conformational properties of these molecules are closely related to each other, and to other mammalian prolactins. Molar extinction and absorptivity values have been obtained at the absorption maximum of each species. In addition, a second molar extinction value has been determined at a particular wavelength found to be different for each, and which appears to be independent of the conformational state of the molecule. These absorptivities are useful in providing accurate prolactin concentrations in the 10(0) to 10(-2) mg/ml range. On incubation with the proteolytic enzyme thermolysin, all three hormones display an initial, short lag period during which little conformational change can be detected by difference absorption spectroscopy. For human and porcine prolactins, subsequent rates of proteolytically induced conformational collapse were found to be essentially identical. However, under similar conditions, equine prolactin loses its conformation significantly more slowly.

Synthesis of adrenal peptide E and some of its biological activities

A synthesis of peptide E, a highly potent, 25-amino acid adrenal opioid peptide containing both a [Met]enkephalin at the NH2-terminus and [Leu]enkephalin sequence at the COOH-terminus, originally isolated from bovine adrenal medulla [D. L. Kilpatrick, T. Taniguchi, B. N. Jones, A. S. Stern, J. E. Shively, J. Hullihan, S. Kimura, S. Stein, and S. Udenfriend (1981) Proc. Natl. Acad. Sci. USA 78, 3265-3268], is reported. The synthesis was accomplished by the solid-phase method employing the 4-(aminoacyloxymethyl)phenylacetamidomethyl(Pam)-copoly(styrene-1% divinylbenzene) resin. Two synthetic strategies (N-indole formyl protected vs unprotected tryptophan) were followed and results compared and evaluated. It was determined that peptide E prepared with protection of tryptophan (residues 13 and 14) was preferred and gave final product that was readily purified by HPLC. The biological activity of the synthetic material was found to be equivalent to the reported activity of the natural compound.

Peptide E: opiate receptor binding profile in the rat brain membrane assay. Comparison with beta-endorphin

Beta-endorphin (beta-EP) and peptide E were compared in respect to their binding potency in the rat brain membrane by radioreceptor binding assay using tritiated human beta-EP, [D-Ala2,D-Leu5]-enkephalin (DADLE), dihydromorphine (DHM) and ethylketocyclazocine (EKC) as primary ligands. When the potency of beta h-EP was chosen to be 100%, peptide E was equipotent with beta-EP in displacing DHM (95%) and EKC (103%) less potent for competing with beta h-EP (60%) and least active (7%) for displacing DADLE. It may be concluded that peptide E binds preferentially with the opiate mu and kappa receptors in the rat brain membrane.

Isolation of melanotropins and vasopressin from neuro-intermediate lobes of bovine pituitary glands. A simplified procedure

A simplified procedure for the isolation of alpha-melanotropin, beta-melanotropin and arginine vasopressin from the acid acetone extract of posterior-intermediate lobes of bovine pituitaries has been described. It involves essentially two steps: gel filtration on Sephadex G-10 and high performance liquid chromatography.

Evidence for tertiary structure in aqueous solutions of human beta-endorphin as shown by difference absorption spectroscopy

The presence of a distinct tertiary structure in aqueous solutions of human beta-endorphin has been demonstrated by difference absorption spectroscopy of thermolysin digests of the hormone and synthetic analogues. The results demonstrate that the alpha-amino group of Tyr1, Lys28, and some residue(s) between Thr6 and Ser10 are involved in forming and stabilizing the folded form of the molecule. Although a peptide corresponding to the first nine residues of human beta-endorphin shows definite evidence of tertiary structure, the pentapeptide methionine-enkephalin does not.