Presence of immunoassayable beta-lipotropin in bovine brain and spinal cord: lack of concordance with ACTH concentrations

From Punch to Profile

In this essay an aspect of my research is highlighted that has its roots in the mid seventies with the implementation of the 'Palkovits punch' procedure. This methodology was introduced when radiochemical and radio-immunoassay methods became sufficiently sensitive to measure key molecules for chemical neurotransmission and metabolism in minute amounts of brain tissue. For application of today's laser guided microdissection this knowledge of functional neuro-anatomy is indispensable.

Beta-endorphin and ACTH levels in the perioperative period

1. The purpose of this study was to determine the plasma levels of beta-endorphin (beta-END) and ACTH in the perioperative period, define correlations of hormonal plasma levels with clinical parameters and establish the effect of droperidol premedication on hormonal levels and clinical parameters. 2. Twenty two were assigned to one of two groups: (1) Control (no premedication) and (2) droperidol (7.5 mg im) premedication. 3. Venous blood samples and clinical evaluations were done the day prior to surgery, just prior to induction of anesthesia and 1-1.5 hr postoperatively. 4. The results indicate that (1) expectancy of surgery on arrival to the operating room increases beta-END but not ACTH plasma levels, (2) this increase in beta-END is not affected by droperidol administration and (3) postsurgical stress increases beta-END and ACTH above operating room levels. 5. These results indicate that although beta-END and ACTH are both produced by the pituitary and derived from a common precursor, the type of stimuli (pre- versus postsurgical stress) seems to differentially affect their plasma levels.

Immunolocalization of beta-lipotropin in the inner ear of the guinea pig

The occurrence of beta-lipotropin (beta-LTH) immunoreactive material was investigated in the inner ear of newborn and juvenile guinea pigs by means of Sternberger's PAP technique. Unlike met5-enkephalin and endorphin, beta-LTH could not be found in the organ of Corti but was identified in the spiral ganglion and the neuroepithelium of the crista ampullaris.

Opiate-like and adrenocorticotrophin-like materials in equine pancreas

Equine pancreatic acetone powder was extracted with an acetone-water-HCl mixture. An acid acetone powder resulted by adding a copious volume of acetone to the extract. The powder was subjected to salt fractionation, gel filtration and chromatography on CM-cellulose. Steroidogenic activity, ACTH-like immunoreactivity and opiate receptor binding activity were distributed among the CM-cellulose chromatographic fractions derived from material unretarded as well as from material retarded on Sephadex G-25. The data indicates a separation of steroidogenic and opiate receptor binding activities, and the presence of opiate-like molecules with different affinities of binding to mu and delta opiate receptors.

beta-Endorphin in neuroblastoma x glioma hybrid cells

Acid extracts from mouse Neuroblastoma x rat Glioma hybrid cells have been purified by means of Sep-Pak C-18 and fractionated by high performance liquid chromatography. Each fraction has been submitted to a sensitive beta-endorphin radioimmunoassay and an immunoreactivity peak at camel beta-endorphin retention time was found.

Dopamine inhibits the release of immunoreactive beta-endorphin from rat hypothalamus in vitro

Mediobasal hypothalamus tissue (MBH) from adult male rats was incubated in Krebs-Ringer bicarbonate medium (KRB). KRB was changed at 15 min intervals and the concentration of immunoreactive beta-endorphin (beta-ENDi) in the medium was measured by radioimmunoassay. Incubation of MBH tissue in normal KRB resulted in a constant release rate of beta-ENDi of approximately 1% of the tissue content per h. KRB containing 45 mM K+ causes a two fold increase in the release rate of beta-ENDi which was Ca2+ dependent. Dopamine (0.01-1.0 microM) inhibits both the spontaneous and the K+-stimulated release of beta-ENDi in a dose related manner. The dopamine receptor blocking agent haloperidol prevents this inhibitory effect of dopamine. The selective D-1 receptor agonist SKF 38393 does not affect the release rate of beta-ENDi; whereas the selective D-2 receptor agonist LY 141865 inhibits both the spontaneous and K+-stimulated release of beta-ENDi. The effects of LY 141865 can be blocked by (-)-sulpiride, a selective D-2 receptor antagonist. Norepinephrine only weakly inhibits the K+-stimulated release of beta-ENDi, an effect that can be blocked by haloperidol but not by the alpha-adrenoceptor blocker phentolamine. At concentrations tested (0.01-1.0 microM), isoproterenol, 5-hydroxytryptamine, carbachol and 8-Br-cAMP (1.0 microM) do not affect beta-ENDi release. It is concluded that dopamine can inhibit the release of beta-ENDi from hypothalamic neurons via a D-2 receptor mechanism.

Brain and pituitary beta-endorphin levels at different developmental stages of the rat

beta-Endorphin-like immunoreactivity in whole brains of Sprague-Dawley rat fetuses of different gestational ages was measured by radioimmunoassay and found to increase throughout the gestational period studied. The immunoreactivity in various brain parts (forebrain, midbrain, hindbrain, hypothalamus and pituitary) of late prenatal, early postnatal, young mature and retired breeder rats was also determined. In all the brain parts studied, a maximum in the content and concentration of beta-endorphin-like immunoreactivity was attained when the rats were about 3-4 months old.

Tissue distribution of messenger RNAs coding for opioid peptide precursors and related RNA

All of the endogenous opioid peptides thus far identified are derived from three types of precursors, i.e. the corticotropin/beta-lipotropin precursor, preproenkephalin A and preproenkephalin B. Poly(A)-containing RNA from various bovine and porcine tissues has been subjected to blot hybridization analysis with the use of cDNA probes specific for the three opioid peptide precursors. Analysis with a corticotropin/beta-lipotropin precursor cDNA probe has revealed, in addition to the pituitary mRNA, a smaller hybridizable RNA species present in bovine extrapituitary tissues, such as the adrenal medulla, thyroid, thymus, duodenum and lung. The hypothalamus contains both these RNA species. DNA complementary to the smaller RNA species from the bovine adrenal medulla has been cloned. Analysis of the cloned cDNA, in conjunction with endonuclease S1 mapping of poly(A)-rich RNA from the adrenal medulla, has indicated that the smaller RNA species represents the 3'-terminal 712-729 nucleotides, excluding the poly(A) tail, of the pituitary corticotropin/beta-lipotropin precursor mRNA, having heterogeneous start sites. Analysis with a preproenkephalin A cDNA probe has shown the presence of hybridizable RNA in the bovine hypothalamus, duodenum and pituitary neurointermediate lobe in addition to the adrenal medulla. The hybridizable RNA species from all these tissues are indistinguishable in size. RNA hybridizable with a preproenkephalin B cDNA probe has been found in the porcine spinal cord and ileum besides the hypothalamus, and these RNA species exhibit an indistinguishable size. The results presented indicate that each opioid peptide precursor is synthesized in different tissues.

Progressive impairment of CSF beta-EP levels in migraine sufferers

Common migraine (CM) is an evolutive disease characterized by a progressive increase in the number of attacks and a consequent reduction in the free periods, eventually reaching a state of continuous migraine with interparoxysmal headache (MIH). To evaluate the role of central pro-opiocortin-related peptides in the pathogenesis of the disease, cerebrospinal fluid (CSF) levels of beta-lipotropin (beta-LPH), beta-endorphin (beta-EP) and ACTH were measured in two groups of migraine sufferers with increasing severity of the disease (CM and MIH), and in healthy controls. ACTH values were similar in the 3 groups, while beta-LPH levels were significantly lower (P less than 0.005) in patients affected by MIH (10.4 +/- 8.6 fmol/ml) than in patients with CM (35.7 +/- 8.3) and in controls (32.9 +/- 15.33). beta-EP levels were closely correlated with the severity of the disease: they decreased significantly from those found in healthy controls (86.1 +/- 37 fmol/ml) to those of CM sufferers (38.5 +/- 3.5; P less than 0.005) and showed a further significant fall (P less than 0.01) to the lowest levels which were found in MIH patients (14.8 +/- 9.8). These data showing that the progressive evolution of migraine is concomitant with a progressive impairment in the CSF levels of beta-EP, sustain the concept that non-organic central pain is related to a reduced activity of the neurons responsible for the CSF content of beta-EP.

Corticotropin/lipotropin common precursor-like material in normal rat extrapituitary tissues

A Mr 26,000 corticotropin (ACTH)-like material is present in glacial acetic acid extracts of all normal rat extrapituitary tissues. In the present study, beta-melanotropin (beta-MSH) immunoactivity was detected in glacial acetic acid extracts of normal rat extrapituitary tissues. beta-MSH immunoactivity was also present in all extracts (mean +/- SEM, fmol/mg of protein): brain, 71.0 +/- 16.3; stomach, 11.5 +/- 1.6; kidney, 8.9 +/- 0.8; colon, 8.2 +/- 1.1; small intestine, 6.5 +/- 1.1; liver, 4.3 +/- 0.5; and heart, 3.2 +/- 0.5. Except in brain extracts, beta-MSH and ACTH immunoactivities of tissue extracts were strongly correlated to each other (r = 0.79; n = 42). When tissue extracts (except brain) were passed through a Sephadex G-75 (superfine) column, ACTH and beta-MSH immunoactivities were eluted in a single peak corresponding to Mr 26,000. In contrast, for brain extracts, the MrS of major peaks of ACTH and beta-MSH immunoactivities were 4,500 and 8,000, respectively; a smaller peak of Mr 26,000 ACTH/beta-MSH-like material was also eluted. Specific anti-ACTH immunocolumns, which did not bind purified synthetic beta-MSH, adsorbed both ACTH and beta-MSH immunoactivities of all tissue extracts except those of brain. One-third of the beta-MSH immunoactivity in brain extracts adsorbed to the anti-ACTH immunocolumn, but two-thirds of beta-MSH immunoactivity passed through the column. We conclude that ACTH and beta-MSH immunoactivities are present in all normal rat extrapituitary tissues and exist in most tissues on the same molecule. This Mr 26,000 molecule is closely related to the pituitary ACTH/beta-lipotropin common precursor.

Circadian variation of beta-endorphin-like immunoreactivity in neurointermediate pituitary

Immunoreactive beta-endorphin-like activity (-IR) and ACTH-IR were determined in rat pituitary lobes and plasma at 4-hr intervals over a 24-hr period. In addition, we measured beta-endorphin-IR in discrete hypothalamic nuclei, and plasma corticosterone levels at the same time points. Significant and replicable circadian variation was detected only in concentrations of beta-endorphin-IR in neurointermediate pituitary and in plasma corticosterone concentrations.

Ontogenesis of opiate binding sites and radioimmunoassayable beta-endorphin and enkephalin in regions of rat brain

The postnatal changes in the levels of radioimmunoassayable enkephalin and beta-endorphin, as well as the densities of [3H]methionine-enkephalin and [3H]naloxone binding sites in rat cerebellum, brainstem and whole forebrain were determined. The opiate peptides and the opiate binding sites reached their highest levels at the first week postpartum in the cerebellum, at the second week in the brainstem and at the third week in the whole forebrain. This finding is in line with the developmental profiles of other well-established neuronal pathways which also showed a caudal-to-rostral sequence of development. Moreover, there was a close relationship between the elevation and decline in the amounts of opiate binding sites and in the levels of opiate peptides in each brain region. These observations are consistent with other evidence which suggests that enkephalin and beta-endorphin are functioning as neurotransmitters or neuromodulators in the central nervous system.

Immunoreactive beta-endorphin in the hypothalamus of female rats: changes in content and release during prepubertal development

Female Wistar rats of different ages (1-45 days) were used. Extracts were made of the mediobasal hypothalamus (MBH) and beta-endorphin immunoreactivity (beta-ENDi) was quantitated by radioimmunoassay. Low but significant amounts of beta-ENDi (6.5 ng/MBH) were present on the first postnatal day. Hypothalamic beta-ENDi content did not change during the first week but decreased during the second week to a minimum (4.5 ng/MBH) on day 14. Thereafter, beta-ENDi increased rapidly to 13 ng/MBH on day 28 and remained at this level. Gel filtration showed that beta-ENDi substances with chromatographic characteristics identical to those of beta-END and beta-LPH were present in MBHs of 14-, 20- and 45-day-old rats. A beta-ENDi substance, possibly representing beta-END1-27, was nearly absent on day 14, but represented a major component of the MBH of the 45-day-old rat. In vitro incubation of MBH resulted in spontaneous release of beta-ENDi. Depolarization of neuronal membranes by incubation in medium containing 45 mMK+ stimulated beta-ENDi release. Both the spontaneous and K+-stimulated release of beta-ENDi were low on day 10 but reached postpubertal levels on day 20. These observations lead us to propose that the beta-ENDi-containing neurons in the hypothalamus of developing female rats rapidly mature between 14 and 20 days after birth. This may be causally related to the rapid decrease in circulating FSH levels that occurs during this period.

Isolation and properties of beta-endorphin-(1-27)-like peptide from bovine brains

A beta-endorphin-(1-27)-like peptide was isolated from bovine cerebral hemisphere extracts by gel filtration, ion-exchange chromatography, high performance liquid chromatography and paper electrophoresis. The peptide had tyrosine as the amino-terminal residue and its amino acid composition was nearly identical to that of equine pituitary beta-EP-(1-27). It had also the same mobility as equine pituitary beta-EP-(1-27) in paper electrophoresis. In radioimmunoassay and opiate receptor-binding assay, the brain peptide had 50% activity when compared with human beta-endorphin-(1-27). Evidence for the occurrence of NH2-acetylated form of beta-endorphin-(1-27) is also presented.

Distribution of beta-endorphin-related peptides in rat pituitary and brain

beta-Endorphin, the most potent known naturally occurring analgesic agent, is found in pituitary and brain in company with a series of structurally and biosynthetically related peptides that are essentially devoid of opiate activity. In studies of beta-endorphin it is important to discriminate between the active and inactive forms of the peptide. This review describes the use of chemical and immunological methods for localizing the peptides in the tissues, extracting and resolving the peptides by chromatography, and determining the concentrations of the peptides by radioimmunoassay. These approaches have allowed the distribution of beta-endorphin and its related peptides to be assigned unequivocally in regions of rat pituitary and brain. It has been found that the multifunctional corticotropin-endorphin prohormone can undergo processing by different mechanisms in different tissues, permitting the intrinsic activities of its fragments to be expressed selectively. The different processing patterns can be attributed to the existence of highly specific enzymes, characteristic of individual cells, which regulate the formation of this potent opiate.

Neuroanatomical methods for the quantitative evaluation of coexistence of transmitters in nerve cells. Analysis of the ACTH- and beta-endorphin immunoreactive nerve cell bodies of the mediobasal hypothalamus of the rat

A new statistical approach has been introduced to study in a quantitative way the coexistence of two neuromodulators in nerve cell bodies. The method has been exemplified on the ACTH-like and beta-endorphin-like immunoreactive nerve cell bodies of the mediobasal hypothalamus demonstrated by means of indirect immunofluorescence methodology. The method is based on the analysis of 3 adjacent sections which, in a random way, are stained with antiserum against neuromodulator 1, against neuromodulator 2 and with antisera against both neuromodulator 1 and neuromodulator 2. It could be shown that some neurons of the mediobasal hypothalamus do not contain at a detectable level both ACTH- and beta-endorphin-like immunoreactivity. The present method also involves an analysis of the two nerve cell groups by means of a morphometric procedure to collect additional information on the extent of coexistence. Thus, by this approach the gravity centers of the two cell groups can be calculated. The distances between the two gravity centers of the ACTH and beta-endorphin positive cell groups were significantly different at certain levels. The present method offers unique possibilities in increasing our understanding of the functional significance of coexistence of neuromodulators in one and the same nerve cell body since it makes possible a quantitative evaluation of coexistence. The usefulness of the present method is illustrated by the findings of a possible differential synthesis of ACTH- and beta-endorphin-like material in certain cell bodies of the mediobasal hypothalamus.

The Mr 80,000 common forms of neurophysin and vasopressin from bovine neurohypophysis have corticotropin- and beta-endorphin-like sequences and liberate by proteolysis biologically active corticotropin

We have tested the hypothesis that the high M(r) forms common to both neurophysin and vasopressin detected in bovine neurohypophysis extracts (Nicolas, P., Camier, M., Lauber, M., Masse, M.-J. O., Möhring, J. & Cohen, P. (1980) Proc. Natl. Acad. Sci. USA 77, 2587-2591) might also contain the sequences of other known neuropeptides. The following evidence indicates that corticotropin- and beta-endorphin-like sequences are associated with similar high M(r) forms and are included in these M(r) 80,000 molecules. During the fractionation steps of high M(r) material, both corticotropin and beta-endorphin immunoreactive species were found to coelute with the neurophysin and vasopressin ones, either under M(r) 140,000 (in 0.1 M formic acid) or M(r) 70,000-80,000 (in 6 M guanidine) elution volumes. Corticotropin immunoreactivity was found to cofocus at pIs 6.05 and 5.8 with the M(r) 80,000 neurophysin-containing species. This material was submitted to affinity chromatography on purified anti-neurophysin antibodies covalently attached to Sepharose 4B. Both the corticotropin and beta-endorphin immunoreactivities, together with the neurophysin and vasopressin immunoreactivities, were retained on the immunoadsorbent and codesorbed by either a drastic pH change or by selective displacement with an excess of neurophysin. Comparison of the tryptic-digest maps of either the M(r) 68,000 fragment immunoprecipitated by anti-corticotropin antibodies or the M(r) 68,000 fragment released after precipitation of the M(r) 80,000 species by anti-neurophysin antibodies indicated large sequence homologies. Exposure of either the M(r) 80,000 or 68,000 components to mild proteolytic activities resulted in the formation of lower-size fragments. The resulting corticotropin-like immunoreactive material, recovered under the elution volume of standard (125)I-labeled corticotropin-(1-24), was tested for its ability to activate glucocorticoid biogenesis by the amphibian interrenal tissue (adrenal) in perifusion. It was found to exhibit a noticeable activity qualitatively undistinguishable from the one of the reference human corticotropin-(1-39). The name neurohypophyseal "coenophorin" (from the Greek word for common) is proposed for this class of M(r) 80,000 polypeptides that might represent the common precursor store-house for a set of neuropeptides produced in the hypothalamo-neurohypophyseal tract.

Effect of hypophysectomy and pituitary stalk transection on alpha-melanocyte-stimulating hormone-like immunoreactivity in the brain of the frog, Rana ridibunda Pallas

The existence of an alpha-MSH-like molecule in the frog brain led us to investigate the role of the pituitary gland in the maintenance of the alpha-MSH content in 3 different regions of the brain. Acetic acid extracts of hypothalamus, rhombencephalon and telencephalon were analyzed by means of a highly specific radioimmunoassay for alpha-MSH in normal, sham-operated, pituitary disconnected and hypophysectomized frogs. Transection of the pituitary stalk gave rise to a significant decrease in alpha-MSH content in the intermediate lobe of the pituitary gland (-71% after 3 days), but did not affect alpha-MSH content in the distal lobe or in the brain. Eight days after total hypophysectomy, an alpha-MSH immunoreactive compound, co-eluting with synthetic alpha-MSH on Sephadex G-25, was found in the 3 brain regions studied. Removal of the whole pituitary gland did not significantly modify alpha-MSH content in the hypothalamus and the telencephalon. A slight increase in alpha-MSH was even observed in the rhombencephalon of hypophysectomized animals. Furthermore, no modification in alpha-MSH immunoreactivity occurred in any region of hypophysectomized animals. These results demonstrate the existence of alpha-MSH-like material in the brain of Rana ridibunda and establish that brain alpha-MSH in the frog is not of pituitary origin.

Release of beta-lipotropin and beta-endorphin from rat hypothalami in vitro

Hypothalamic tissue extracts of rats were chromatographed and beta-endorphin immunoreactivity (beta-Endi) was measured. The two major peaks of beta-Endi co-eluted with beta-lipotropin (beta-LPH) and beta-End respectively. Hypophysectomy caused a local decrease of beta-LPH and beta-End concentrations in the mediobasal hypothalamus. During superfusion of hypothalamic tissue blocks in vitro, membrane depolarization by electric stimulation or 45 mM k+ induced a Ca2+-dependent release of both beta-LPH and beta-End.

The regional distribution of gamma 3-melanotropin-like peptides in bovine brain is correlated with adrenocorticotropin immunoreactivity but not with beta-endorphin

Immunoreactive (IR)-gamma 3-melanotropin (MSH), -adrenocorticotropin (ACTH) and -beta-endorphin in various areas of bovine brain were measured with their respective radioimmunoassays (RIA). The concentrations of IR-gamma 3-MSH were almost the same as those of IR-ACTH in most areas. Furthermore, in all brain regions, the concentrations of both peptides were lower than those of IR-beta-endorphin. The highest concentration of IR-gamma 3-MSH was found in hypothalamus, followed by thalamus, midbrain and striatum. Gel permeation chromatographic studies showed that the main gamma 3-MSH-like peptide in the hypothalamus, striatum and midbrain was a small form, whose molecular weight is about 4500. These brain gamma 3-MSH-like peptides were also found to be glycosylated.

Isolation and characterization of beta-endorphin-like peptides from bovine brains

Four beta-endorphin-like peptides from bovine brain extracts have been identified by their behavior in CM-cellulose chromatography, gel filtration, high-performance liquid chromatography, and radioimmunoassay. Two of them have been isolated in sufficient quantity for amino acid analysis, radioimmunoassay, and radioreceptor assay. One peptide has an amino acid composition nearly identical to that of beta-endorphin with 56% of the radioimmunoreactivity and 2.3% of the potency in the radioreceptor assay of beta-endorphin. The amino acid content of the other beta-endorphin-like peptide is very different from that of bovine beta-endorphin but it has 47% of the radioimmunoreactivity and 1% of the potency in the radioreceptor assay of beta-endorphin.

Endogenous opiates: through 1978

The discovery of receptors in the brain for opiates and the structure of the endogenous peptides for these receptors has led to an explosion of interest in this field. The present review is the first of an annual series. It summarizes many of the highlights of research with opiate peptides published with a date of 1978 or earlier.

Regional distribution of methionine-enkephalin- and beta-endorphin-like immunoreactivity in human brain and pituitary

Concentrations of methionine-enkephalin- (Met-enkephalin) and beta-endorphin-like immunoreactivities were determined in 33 areas of human brain and pituitary using highly sensitive radioimmunoassays in combination with affinity chromatography for the purification of beta-endorphin. It was found that they have quite different distribution patterns, suggesting the existence of both endorphins in independent systems in the central nervous system. Determination of Met-enkephalin and beta-endorphin immunoreactivities in chronic alcoholics and opiate-dependent subjects revealed no gross changes in comparison to the normal subjects.

Pituitary hormones in brain: where, how, and why?

Peptide and protein hormones usually considered as being of pituitary origin have been detected within the central nervous system by means of radioimmunoassay, bioassay, and immunocytochemical techniques. Intracerebral administration of some of these hormones or fragments thereof elicit behavioral responses, suggesting that they may have a physiological role similar to that described for other peptidergic neurotransmitter or neuromodulator substances. Evidence available for some of these hormones indicates that they are synthesized within the central nervous system and that their regulation may differ from that of their pituitary counterparts.

Pituitary-brain vascular relations: a new paradigm

Vascular casts of the pituitary gland have demonstrated a paucity of veins extending from the adenohypophysis to the systemic circulation and have suggested that some adenohypophyseal venous blood returns to the neurohypophysis. The neurohypophyseal capillary bed may function as a vascular switch and in this article a series of 14 questions are proposed regarding the vascular dynamics of the pituitary. Together these questions raise the larger question, namely, whether pituitary hormones are transported directly to the brain to modify brain function?