Decapeptide luteinizing hormone releasing hormone in ovine pineal gland

Generation of the melatonin endocrine message in mammals: a review of the complex regulation of melatonin synthesis by norepinephrine, peptides, and other pineal transmitters

Melatonin, the major hormone produced by the pineal gland, displays characteristic daily and seasonal patterns of secretion. These robust and predictable rhythms in circulating melatonin are strong synchronizers for the expression of numerous physiological processes in photoperiodic species. In mammals, the nighttime production of melatonin is mainly driven by the circadian clock, situated in the suprachiasmatic nucleus of the hypothalamus, which controls the release of norepinephrine from the dense pineal sympathetic afferents. The pivotal role of norepinephrine in the nocturnal stimulation of melatonin synthesis has been extensively dissected at the cellular and molecular levels. Besides the noradrenergic input, the presence of numerous other transmitters originating from various sources has been reported in the pineal gland. Many of these are neuropeptides and appear to contribute to the regulation of melatonin synthesis by modulating the effects of norepinephrine on pineal biochemistry. The aim of this review is firstly to update our knowledge of the cellular and molecular events underlying the noradrenergic control of melatonin synthesis; and secondly to gather together early and recent data on the effects of the nonadrenergic transmitters on modulation of melatonin synthesis. This information reveals the variety of inputs that can be integrated by the pineal gland; what elements are crucial to deliver the very precise timing information to the organism. This also clarifies the role of these various inputs in the seasonal variation of melatonin synthesis and their subsequent physiological function.

Characterization of gonadotropin-releasing hormone (GnRH)-immunoreactive protein in the rat pineal gland

The aim of the present study was to characterize GnRH-like substance(s) in the rat pineal gland using a monoclonal antibody, LRH13, as a probe. The epitope of LRH13 is between 2nd and 5th amino acid residues of the mammalian GnRH, and its immunological characters were previously defined by us. LRH13 could show strong immunological signal on the rat pineal gland. Immunoblot after SDS-PAGE of the pineal gland preparations showed a LRH13 immunoreactive band with apparent mol wt 52 kilo-Dalton (kD), which is much bigger than that of hypothalamic GnRH precursor (10 kD). The 52 kD protein, however, was detected from insoluble fraction of the pineal homogenate and liberated from the fraction by Triton X-100 (2%) treatment. On the other hand, NaCl (140 mM and 500 mM) or EDTA (10 mM) treatment failed to liberate. Two-dimensional gel electrophoresis showed that the 52 kD protein is a mixture of two proteins with different isoelectric points (pI approximately 6.8 and 7.0). Both proteins showed identical patterns of peptide mapping by V8 protease digestion, and they might be originated from the same peptide. These results suggest that the rat pineal GnRH-immunoreactive substance has a unique property as a membrane associate protein.

Polygenic expression of gonadotropin-releasing hormone (GnRH) in human?

A non-mammalian lamprey-like gonadotropin-releasing hormone (lGnRH) has been detected in human hypothalami using a combination of immunocytochemistry, high performance liquid chromatography and radioimmunoassay. The hypothalamic distribution of immunopositive lGnRH neurons is similar to that observed for those containing the mammalian gonadotropin-releasing hormone (mGnRH), indicating a possible role for this newly identified peptide in the regulation of pituitary function. Our data suggest the existence of a separate gene for lamprey-like GnRH in humans. Confirmation of the exact nature and role of this newly detected form of GnRH will require future isolation and sequence analysis. The possibility that polygenic expression of a given peptide may be a common phenomenon even in higher mammals is discussed.

Studies on a high molecular weight luteinizing hormone release stimulating factor of the ovine pineal gland

Former work has shown that crude extracts of ovine pineal glands probably exert a stimulating activity on the release of gonadotropins of anterior pituitaries in vitro. By aqueous extraction followed by ultrafiltration through anisotropic membranes high Mr (above 100,000 daltons) fractions were obtained, which exhibit a stimulating effect on the levels of gonadotropins in the medium of either cultured pituitary cells or anterior hemipituitaries in short-term culture. Partial purification of a pineal luteinizing hormone release stimulating factor was accomplished by Sephadex G-150 filtration with a biopotency of 226 +/- 23 micrograms LH-RP-1 equivalents per mg protein and without an affinity for binding to anti-LHRH or anti-LH antibodies. The present data substantiate that high Mr forms, slightly heavier than authentic pituitary LH (Mr 23,000 daltons) and therefore not identical to the hypothalamic decapeptide LH-RH, represent ovine pineal factors which can increase the concentration of LH in the medium of cultured anterior pituitaries, but does not influence the secretion of prolactin in vitro.

Identification of Gln8-GnRH and His5,Trp7,Tyr8-GnRH in the hypothalamus and extrahypothalamic brain of the ostrich (Struthio camelus)

Gonadotropin-releasing hormone (GnRH) molecular forms were studied in extracts of ostrich hypothalamus and extrahypothalamic brain using high performance liquid chromatography, radioimmunoassay with region-specific antisera and assessment of luteinizing hormone (LH)-releasing activity using chicken dispersed pituitary cells. Two molecular forms of GnRH with chromatographic, immunological and biological properties identical to those of Gln8-GnRH and His5,Trp7,Tyr8-GnRH were demonstrated in both the hypothalamic and extrahypothalamic brain extracts. A greater proportion of His5,Trp7,Tyr8-GnRH was present in the hypothalamus than in extrahypothalamic brain. It is likely that these two forms of GnRH are present in all bird species, since the chicken and the ostrich have evolved separately.

Bovine pineal antireproductive tripeptide binds to luteinizing hormone-releasing hormone: a model for peptide modulation by sequence specific peptide interactions?

We report results of chromatographic, pH titration and nuclear magnetic resonance (NMR) spectroscopy studies demonstrating that the bovine pineal antireproductive tripeptide, Thr-Ser-Lys (BPART), binds to luteinizing hormone-releasing hormone (LHRH) at a site comprised of LHRH 2-5 (His-Trp-Ser-Tyr). BPART and LHRH have been shown to be antagonists in vitro. The binding constant is ca. 2 X 10(3)/mole. An NMR study of fifty other peptide pairs demonstrates that the binding is sequence and residue specific. The binding provides evidence of the amino acid pairing hypothesis, and suggests the possibility of modulation of one peptide by directly binding with another peptide.

Identification of His5,Trp7,Tyr8-GnRH (chicken GnRH II) in amphibian brain

GnRH immunoreactive and bioactive peptides in Xenopus laevis brain extract were investigated by high performance liquid chromatography (HPLC), radioimmunoassay with region-specific antisera raised against GnRH (mammalian), His5,Trp7,Tyr8-GnRH (chicken II) and Tyr3,Leu5,Glu6,Trp7,Lys8-GnRH (lamprey), and by assessment of biological activity. Two immunoreactive peptides eluted in the same positions as GnRH and His5,Trp7,Tyr8-GnRH respectively in HPLC systems which were specifically designed to separate four known natural vertebrate GnRHs (mammalian, chicken I and II, salmon). The immunological properties of these two immunoreactive peaks, determined by relative interaction with three region-specific antisera raised against mammalian GnRH and two specific His5,Trp7,Tyr8-GnRH antisera, were identical to those of GnRH and His5,Trp7,Tyr8-GnRH. The immunoreactive peak co-eluting with His5,Trp7,Tyr8-GnRH represented approximately one-third of the total brain GnRH. Both immunoreactive peaks stimulated luteinizing hormone (LH) release in a chicken dispersed pituitary cell bioassay, and the amounts of LH release stimulated by the two peaks were appropriate for these peaks being GnRH and His5,Trp7,Tyr8-GnRH. A small hydrophobic peak with GnRH immunoreactivity eluted in the same position as Trp7,Leu8-GnRH (salmon), while Gln8-GnRH (chicken I) and lamprey GnRH were not detected. Two additional rather hydrophilic peptides cross-reacted with a COOH-terminus-directed antiserum and had LH-releasing activity. LH-releasing activity was also detected in hydrophobic HPLC fractions. In summary, these data provide evidence for the presence of both GnRH and a second peptide with properties identical to His5,Trp7,Tyr8-GnRH in X. laevis brain.(ABSTRACT TRUNCATED AT 250 WORDS)

The isolation and measurement of luteinizing hormone-releasing hormone (LHRH) from the rat testis

Although LHRH has been implicated in the direct control of rat Leydig cell function, LHRH has not been previously detected in the rat testis. An optimized fractionation procedure, which involved acid extraction, bulk fractionation on ODS-silica, extraction in chloroform/ethanol, ether extraction, gel filtration on Sephadex G-15 and RP-HPLC, was employed to isolate LHRH from lyophilized adult rat testes. LHRH activity was assessed by an in vitro LHRH bioassay system employing rat anterior pituitary cells in monolayer culture and several radioimmunoassays for LHRH. LHRH recoveries were monitored by the addition of exogenous LHRH to some samples of lyophilized testes prior to extraction. LHRH bioactivity was non-detectable in the LHRH region of the gel filtration profile of testis extracts in the absence of exogenous LHRH; however, using the most specific LHRH RIA procedure, LHRH immunoactivity which co-chromatographed with LHRH following RP-HPLC was found in all extracts. Based on an average LHRH recovery of 31.0%, as determined from the extracts containing exogenous LHRH, the level of endogenous LHRH immunoactivity in the extracts was determined to be equivalent to 5.6 pg LHRH/g dry weight or 1.0 pg LHRH/testis. These results indicate that the levels of LHRH in the adult rat testis are considerably less than those of the hypothalamus. Based on these findings a simplified fractionation/assay procedure with sufficient sensitivity can be devised for the quantitation of testicular LHRH as a means of clarifying its physiological role in gonadal function.

Multiple molecular forms of gonadotropin-releasing hormone in teleost fish brain

Gonadotropin-releasing hormone (GnRH) immunoreactive peptides in extracts of hake (Merluccius capensis) and tilapia (Tilapia sparrmanii) brain were investigated by high performance liquid chromatography (HPLC) and radioimmunoassay with region-specific antisera. In hake brain, content and concentration of GnRH was higher in the pituitary gland than in the hypothalamic lobes or extrahypothalamic brain. Hake pituitary gland GnRH was purified by six consecutive HPLC systems. The major GnRH molecular form co-eluted with salmon brain GnRH (Trp7, Leu8-GnRH) in four different HPLC systems which were specifically designed to separate the four natural vertebrate GnRHs (mammalian, salmon, chicken I and II). The immunoreactive peak in the final purification step had a retention time identical to that of Trp7, Leu8-GnRH and an UV absorbance (280 nm) peak appropriate for two tryptophan residues in the peptide, as in Trp7, Leu8-GnRH. Six additional less hydrophobic forms of GnRH were detected. Tilapia brain extract contained two major GnRH molecular forms which had identical retention times to chicken GnRH I (Gln8-GnRH) and Trp7, Leu8-GnRH in an HPLC system which separates the natural vertebrate GnRHs. The immunological properties of these two immunoreactive peaks, determined by relative interaction with four region-specific GnRH antisera raised against vertebrate GnRHs, were identical to those of Gln8-GnRH and Trp7, Leu8-GnRH. Additional GnRH molecular forms were also detected. In summary, these findings indicate that a major GnRH molecule in hake pituitary gland is Trp7, Leu8-GnRH, while tilapia brain contains both Trp7, Leu8-GnRH and Gln8-GnRH. Additional GnRH molecular forms were detected in both species.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of ovine pineal compounds prepared under red or green light on the activity of male rat anterior pituitaries in vitro

A high molecular weight fraction XM100R (MW A 100,000) was prepared by ultrafiltration from ovine pineals using two different extraction methods under red light conditions (lambda greater than 600 nm). This fraction stimulates the release of radioimmunologically active luteinizing hormone (LH) of anterior pituitaries in vitro. The ultrafiltration fraction PM30R (MW greater than 30,000 and less than 100,000) was found to be radioimmunologically active only when the "Bensinger" extraction procedure was applied. However, when comparable fractions were prepared under green light and incubated with half-pituitaries, all the incubation media of the ultrafiltrated fractions, XM100R, PM30R, PM10R (MW greater than 10,000 and less than 30,000) UM2R (MW greater than 1000 and less than 10,000), UM05R (MW greater than 500 and less than 1000) and UM05F (MW greater than 500), reacted with anti-LH. This may mean that under green light conditions the high molecular weight ovine pineal compounds in XM100R are disintegrated and/or split up into small molecules which can stimulate the release of LH, or crossreact with the anti-LH serum.

Luteinizing hormone-releasing hormone (LH-RH) cells and their projections in the forebrain of the bat Myotis lucifugus lucifugus

Luteinizing hormone-releasing hormone (LH-RH) neurons and their projections were studied by immunocytochemistry in the brains of little brown bats (Myotis lucifugus lucifugus: Chiroptera: Vespertilionidae ) as a first step in the study of relationships between these neurons and the seasonal reproductive events characteristic of this species. The majority of immunoreactive neurons in adult male, adult female, and fetal bats were ovoid bipolar cells with one thin and one thicker process, both of which gave rise to fine varicose fibers. LH-RH-immunoreactive perikarya were concentrated in the region of the arcuate nuclei in all bats examined. Perikarya were also consistently found dispersed in the mammillary region, anterior hypothalamus, preoptic areas, septum, diagonal band of Broca, and olfactory tracts; they were occasionally observed in the dorsal hypothalamus, organum vasculosum of the lamina terminalis (OVLT), habenula, amygdala, and cingulate gyrus. LH-RH-immunoreactive fibers projected heavily to the median eminence, infundibular stalk, and posterior pituitary. In extrahypothalamic areas, these fibers were especially abundant in the stria medullaris/habenula and stria terminalis/amygdala, but also contributed to the diagonal band of Broca and the olfactory tracts. Immunoreactive fibers that may be components of many different pathways clustered in the rostral septum and permeated the medial hypothalamus. LH-RH-containing fibers frequently entered the subfornical organ, but were observed less often in the OVLT and only occasionally in the pineal. The organization of the LH-RH system in the little brown bat resembles that of primates, but differs considerably from that in the rat. Anatomical characteristics of the LH-RH system in bats thus suggest that this animal may be a particularly suitable species for further study of neuroendocrine control of reproductive function as it may relate to primates, including humans.

Presence and distribution of radioimmunoassayable LHRH in the European eel, Anguilla anguilla

Eel brain contains a factor which exhibited a complete cross-reaction in a radioimmunoassay (RIA) for mammalian luteinizing hormone-releasing hormone (LHRH) and which exhibited a behavior similar to that of synthetic mammalian LHRH on Sephadex G-25. Eel brains contained 920 +/- 135 pg of this LHRH-like immunoreactive factor (IR-LHRH); 75% of immunoreactivity was present in the di- and mes-encephalon, 21% in the telencephalon and 4% in the hind-brain. Thus, IR-LHRH in eel brain exhibited a much wider distribution than in mammalian brain. Pituitary also contained a large amount of IR-LHRH (304 +/- 69 pg) at a concentration even higher than in median hypothalamic lobe; this result is probably related to the fact that, in teleost, median eminence is included into the pituitary. An immunoreactive substance was also present in the blood. In conclusion, the lack of sexual development and the low gonadotropic function in the eel, are apparently not related to an absence of LHRH.

Comparison of some peptidic and proteic ovine pineal fractions with a bovine pineal E5 fraction

Using rather simple and mild extraction and separation methods, three ovine pineal fractions (XM 300 R-PP7.2' and PP7.2 S) were obtained, which contain peptidic/proteic substances and which show fluorescence characteristics of indoles. The ovine fractions were compared with the bovine pineal E-5 fraction. The ovine fractions are chemically sensitive to normal laboratory light and stable in red light (lambda greater than 600 nm). Immunologically, these fractions and the bovine E 5 fraction are stable. From the results of radioimmunological experiments it was concluded that the bovine pineal E 5 fraction as well as the ovine pineal fraction XM 300 R-PP7.2 and PP7.2S may contain (a) peptide(s) ending by the same carboxy terminal tripeptide Pro-Arg-Gly(NH2).