Isolation and characterization of alpha-endorphin and gamma-endorphin from single human pituitary glands

Endorphin-like immunoreactivities in uncultured and cultured human peripheral blood mononuclear cells

It has been reported that cells of the immune system produce and release considerable amounts of pro-opiomelanocortin (POMC) -derived peptides in response to coculture with a variety of stimulatory agents. The present study investigated whether extracts of human peripheral blood mononuclear cells (PBMC) contain immunoreactivity for beta-endorphin (beta E) and related peptides. Using four endorphin RIA systems with different specificities, extracts of freshly isolated PBMC and PBMC cultured in the presence or absence of mitogens or of corticotropin releasing factor (CRF) and vasopressin (VP), were analyzed. With a radioimmunoassay (RIA) system directed to the midportion of beta E, immunoreactivity (MP beta E-IR) was readily detectable, although the concentration was extremely low (ca. 200 pg/10(7) cells). beta E immunoreactivity (beta E-IR) and alpha-endorphin immunoreactivity (alpha E-IR), as determined in C-terminally directed RIA systems, were present in even lower concentrations. gamma-Endorphin immunoreactivity (gamma E-IR) was hardly detectable. Of subsets enriched in T-cells, B-cells or monocytes, the highest concentration of MP beta E-IR was detected in extracts of monocytes. Coculture of PBMC with the mitogen Concanavalin A (Con A) or Phytohaemagglutinin (PHA) increased the amount of MP beta E-IR in extracts of the cells. No increase in alpha E-IR, however, was detected, whereas beta E-IR was only increased in extracts of cells cultured in the presence of Con A. No increase, in any of the immunoreactivities, was observed in extracts of PBMC cultured with bacterial lipopolysaccharide (LPS) or with the combination of CRF and VP, both stimuli that have been reported to induce POMC peptides in cultured PBMC. The present data show that human PBMC contain endorphin-like immunoreactivity, but in very small amounts. The extremely low concentrations and the ineffectiveness of LPS and the combination of CRF and VP to increase the endorphin-like immunoreactivity raise questions about the reported capacity of PBMC to synthesize POMC-derived peptides.

Oocyte fertilization in vitro is associated with high follicular immunoreactive beta-endorphin levels

Follicular fluid (FF) levels of immuno reactive beta-Endorphin (i.r. beta-EP), i.r. gamma-Endorphin (i.r. gamma-EP), i.r. alpha-melanocyte-stimulating hormone (i.r. alpha-MSH), androgens and estrogens were measured in 76 preovulatory follicles obtained, after gonadotropin stimulation from 19 women undergoing in vitro fertilization (IVF). The aim of the study was to investigate the relationships existing between peptide contents of FF and both oocyte-cumulus-corona-complex (OCCC) maturity and the success of IVF. Peptides and steroids were measured by RIA after FF extraction with liquid chromatography and ethyl-ether, respectively. Out of the total of 76 oocytes, 52 were fertilized in vitro and 35 of them underwent normal cleavage and were transferred. Among the three peptides, only i.r. beta-EP levels were higher in FF from follicles which contained oocytes that were subsequently fertilized (127.6 +/- 16.2 pmol/L mean +/- SE) than in FF from follicles which contained oocytes that did not subsequently fertilized (62.9 +/- 8.4, p less than 0.04). Independent of subsequent fertilization, i.r. alpha-MSH values in FF were 5 times higher than those of i.r. beta-EP and i.r. gamma-EP. In the presence of a morphologically mature oocyte, FF i.r. gamma-EP levels (165.2 +/- 45.3 pmol/L) were higher than in FF from follicles yielding immature (63.6 +/- 13.5, p less than 0.01) or luteinized (32.7 +/- 9.2, p less than 0.01) oocytes. Steroid levels in FF did not change in relation to oocyte maturity or subsequent oocyte fertilization.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased concentration of alpha- and gamma-endorphin in post mortem hypothalamic tissue of schizophrenic patients

The concentrations of alpha-, beta- and gamma-endorphin were determined by radioimmunoassay in HPLC fractionated extracts of post mortem hypothalamic tissue obtained from schizophrenic patients and controls. The hypothalamic concentration of alpha- and gamma-endorphin was significantly higher in patients than in controls (+72.9% and +50.5% respectively). No difference was found in the concentration of beta-endorphin, the putative precursor of alpha- and gamma-endorphins. These results suggest a deviant metabolism of beta-endorphin in the brain of schizophrenic patients. Whether this phenomenon is related to the psychopathology, or is a consequence of ante mortem farmacotherapy, remains to be established.

Isolation and characterization of beta-endorphin-(1-9) from human and rat pituitaries

Using a radioimmunoassay specific for the carboxyl terminus of beta-endorphin-(1-9) large amounts of beta-endorphin-(1-9)-immunoreactive material was detected in the human pituitary. The major peak of immunoreactivity was purified and characterized by fast atom bombardment-mass spectrometry and Edman degradation sequencing as authentic beta-endorphin-(1-9). In the rat pituitary the highest concentration of beta-endorphin-(1-9) immunoreactivity was in the posterior neurointermediate lobe. This material was identified as N-acetyl beta-endorphin-(1-9) by multiple radioimmunoassays, gel chromatography, and reversed-phase high-performance liquid chromatography. Control experiments determined that beta-endorphin-(1-9) was not formed postmortem or during the extraction procedure. These studies suggest that single lysine residues, similar to single arginine residues, are potential sites of posttranslational processing.

N-acetylated endorphins in ovine anterior pituitary and neuro-intermediate lobe

We have used an antiserum for immunohistochemistry and RIA/RP-HPLC which recognizes all fragments of N-acetylated endorphin (NacEP). In the rat neuro-intermediate lobe (N-IL), in addition to the N-acetylated forms of immunoreactive-beta-endorphin (ir-beta EP) already reported, we have demonstrated Nac beta EP as a minor component. In the sheep pituitary processing of beta EP is markedly different. In the anterior pituitary (AP), staining was indistinguishable with beta EP and NacEP antisera, in contrast with the rat where many fewer AP cells stained with the NacEP antiserum. Secondly, as in the rat, all N-IL cells stained with both antisera; on RP-HPLC, however, the major forms of NacEP in the sheep N-IL were Nac beta EP (approximately 40%), Nac beta EP (approximately 25%) and Nac beta EP (approximately 20%), with Nac beta EP (approximately 2%) as a minor component. A similar profile was seen on RP-HPLC of sheep AP. These data suggest that (1) patterns of processing in sheep AP are similar to those in N-IL, though the extent of acetylation is less and (2) in the sheep pituitary low molecular weight acetylated fragments predominate, in contrast with the rat.

Ontogeny of pituitary beta-endorphin and related peptides in the human embryo and fetus

In this study we evaluated the presence of proopiomelanocortin-related peptides (beta-lipotropin, beta-endorphin, and gamma-endorphin) in five embryos (5 to 10 weeks of pregnancy) and 11 fetal pituitaries (15 to 25 weeks) by means of high-performance liquid chromatography coupled with specific radioimmunoassays. Tissues were collected at laparotomy for ectopic pregnancy (five embryos) or after spontaneous (seven) or prostaglandin-induced (four) abortion. beta-Endorphin and beta-lipotropin were present starting at the seventh week of pregnancy while gamma-endorphin appeared only in the second trimester. During embryonic life opioid activity was limited to the cephalic portion. The three peptides, but little, if any, acetylated 1-31 beta-endorphin, were recognized in the fetal pituitary throughout the second trimester, at which time beta-lipotropin and beta-endorphin showed constant values in spite of increasing gamma-endorphin concentrations. beta-Lipotropin was the predominant peptide in both embryonic and fetal life. In conclusion, the three peptides related to proopiomelanocortin were expressed from the precursor at different times throughout development. By the beginning of the second trimester the pituitary processing of proopiomelanocortin is similar to that of adult life and the functional activity of the anterior lobe seems to prevail over that of the "fetus-related" neurointermediate lobe around the twenty-fifth week of pregnancy.

Desenkephalin-gamma-endorphin restores the impaired sensitivity of hypophysectomized rats to small doses of apomorphine

Hypophysectomized male rats, tested 7 days after removal of the pituitary, showed a reduced sensitivity to small doses of apomorphine. In these rats, subcutaneous (s.c.) treatment with apomorphine (25, 100 or 250 micrograms/kg) did not elicit any reduction in locomotor activity measured 5 min after injection in contrast to that observed in sham-operated control rats. The enhancement of locomotor activity and stereotyped behavior, 20 min after the s.c. administration of apomorphine, was similar in hypophysectomized rats and in control animals. Prolactin does not seem to be implicated in this altered sensitivity, since hyperprolactinaemia induced by pituitary homografts under the kidney capsule did not change the response to apomorphine in hypophysectomized rats. Chronic treatment with desenkephalin-gamma-endorphin (DE gamma E), a beta-endorphin fragment with neuroleptic-like properties, administered s.c. twice a day for 7 days at the dose of 10 micrograms/rat, restored the sensitivity to small doses of apomorphine in the hypophysectomized rats. The data suggest that removal of the pituitary leads to impaired sensitivity of presumably presynaptically located dopamine receptors mediating the effects of small doses of apomorphine without altering the sensitivity of postsynaptically located dopamine receptors that mediate the hypermotility and stereotypy induced by apomorphine. This impaired sensitivity to low doses of apomorphine could be restored by DE gamma E but not by prolactin, supporting the conclusions from previous experiments that DE gamma E and prolactin may selectively interfere with pre- and postsynaptic dopamine receptors respectively.

gamma-Endorphin and schizophrenia: amino acid composition of gamma-endorphin and nucleotide sequence of gamma-endorphin cDNA from pituitary glands of schizophrenic patients

The possibility has been mentioned that a change in the structure is responsible for the deviant behavioral activity of gamma-endorphin in extracts of postmortem brain and pituitary gland samples of schizophrenic patients. This paper describes the investigation of this possibility by means of: amino acid composition analysis of alpha- and gamma-endorphin isolated from a pituitary gland of a schizophrenic patient; and nucleotide sequence analysis of the gamma-endorphin coding region of pro-opiomelanocortin (POMC) mRNA from two other pituitary glands, using the primer extension method. Both methods require no more than a single pituitary to obtain reliable results. alpha- and gamma-endorphin were isolated from an acid extract by gel filtration and two subsequent HPLC steps. In addition, the gamma-endorphin region of beta-endorphin was analyzed by enzymatic cleavage of beta-endorphin and isolation of the resulting fragment. Single-stranded gamma-endorphin cDNA was synthesized by reverse transcriptase using total cellular pituitary RNA and a 5' 32P-labeled oligodeoxyribonucleotide primer (20-mer) hybridizing close to the gamma-endorphin coding region of POMC mRNA. Single-stranded cDNA was digested with restriction enzyme HaeIII which generated a 148 nucleotides long radioactive cDNA fragment containing the gamma-endorphin cDNA sequence. The sequence of the 148 nucleotides fragment was determined. Neither the amino acid composition analysis nor the amino acid sequence derived from the cDNA nucleotide sequence revealed differences between schizophrenics and controls. Thus, no evidence was found for changes in the amino acid sequence of pituitary gamma-endorphin in these analyses, which include 3 cases of schizophrenia.(ABSTRACT TRUNCATED AT 250 WORDS)

N alpha-Acetyl-gamma-endorphin is an endogenous non-opioid neuropeptide with biological activity

N alpha-acetyl-gamma-endorphin (Ac gamma E) was identified in the rat neurointermediate pituitary, based on its immunological properties, comigration with synthetic Ac gamma E on HPLC and resistance to aminopeptidase-M degradation. The peptide appeared to be the main form of gamma-endorphin (gamma E) in this tissue and in brain areas remote from the hypothalamus (hippocampus, septum, amygdala). The anterior pituitary, the hypothalamus and the thalamus contained almost exclusively the non-acetylated form of gamma E. In contrast to gamma E, Ac gamma E was completely devoid of specific affinity for brain opiate binding sites. Yet, the peptide mimicked gamma E in that it potently attenuated passive avoidance behaviour in rats, when injected topically into the nucleus accumbens. It is concluded that Ac gamma E is an endogenous neuropeptide with non-opioid biological activity. N alpha-acetylation may not merely represent a mechanism for the inactivation of opioid activities of endorphins, but rather allow the organism to select specific sets of biological activities that reside in the endorphin structure.

The identification and characterization of alpha-N-acetylated beta-endorphin in the human pituitary gland

By using a radioimmunoassay specific for alpha-N-acetyl beta-endorphin and its C-terminally shortened forms, we have established the presence of immunoreactive alpha-N-acetyl endorphin (irNacEP) in extracts of five postmortem human pituitary glands (2.27 +/- 0.64 ng/gland). This immunoreactivity has been further characterized by subjecting these extracts to reverse-phase high-performance liquid chromatography (RP-HPLC). In all cases the major peaks of irNacEP co-migrated with synthetic human standard alpha-N-acetyl alpha-endorphin (Nac alpha EP), alpha-N-acetyl gamma-endorphin (Nac gamma EP) and Nac beta EP. These studies thus represent the initial demonstration that alpha-N-acetylation of beta-endorphin and its shorter molecular forms occurs in the human pituitary gland.

gamma-Endorphin generating endopeptidase in rat brain: subcellular and regional distribution

beta-Endorphin is converted into the biologically active fragment gamma-endorphin by an endopeptidase which we term "gamma-endorphin generating endopeptidase". Subcellular and regional distributions of this endopeptidase activity in rat brain were studied by a newly developed assay. After subcellular fractionation of rat brain tissue gamma-endorphin generating endopeptidase activity was predominantly recovered in the cytosolic fraction. A 10 to 15 fold lower activity was present in synaptosomes, mitochondria and synaptic membranes. Hardly any endopeptidase activity was detected in nuclei and myelin. The endopeptidase activity in cytosolic and particulate fraction was found throughout brain, pituitary and spinal cord in a rather homogeneous fashion. Cytosolic activity in all brain parts was 10 to 15 fold higher than the activity in the particulate fraction. It is suggested that rather the beta-endorphin distribution than the endopeptidase is restricting for gamma-endorphin production in certain brain parts.