C-fragment of lipotropin--an endogenous potent analgesic peptide.
(57/105)
1 A series of peptides derived from porcine lipotropin was examined for analgesic and other morphine-like properties on infusion into the cannulated third ventricle of cats.2 Lipotropin (LPH 1-91) itself produced no analgesia or other morphine-like effects when infused in a dose of 150 mug.3 C-fragment (LPH 61-91) produced strong long-lasting analgesia when infused in a dose of 10 or 20 mug; on a molar basis the potency was between 90 and 180 times that of morphine. The following morphine-like effects were also produced: shivering leading to fever, vasodilatation of the pinnae, mydriasis, opening of the palpebral fissures, tachypnoea with bouts of panting, vocalization, hyperexcitability, restlessness and catalepsy. All the effects, including analgesia, were abolished by an intraperitoneal injection of naloxone (1 mg/kg).4 Hyperglycaemia, another central effect produced by morphine, was obtained with C-fragment infused in a dose of 60 mug.5 On intravenous injection, C-fragment produced analgesia with a dose of about 200 mug/kg. Administered by this route, C-fragment was again more potent than morphine.6 C'-fragment (LPH 61-87), LPH 61-78 and LPH 61-69, either had no analgesic effect or produced weak short-lasting analgesia when infused in doses up to 100 mug.7 Methionine enkephalin (LPH 61-65) either produced very weak short-lasting analgesia or had no analgesic effect when infused in doses of between 30 and 400 mug.8N-methyl methionine enkephalin amide in which both termini of methionine enkephalin were protected against degradation by exopeptidases produced long-lasting analgesia when infused in doses of 150 to 180 mug; its analgesic potency was approximately 100 times less than that of C-fragment. Blocking only one terminus of methionine enkephalin did not appear to endow the peptide with analgesic properties. The N-methyl pentapeptide amide produced other morphine-like effects of which the most striking was catalepsy. All the effects were abolished by intraperitoneal naloxone (1 mg/kg). (+info)
Effects of proopiomelanocortin-derived peptides, methionine-enkephalin and forskolin on the maturation of ovine fetal adrenal cells in culture.
(58/105)
The present study examined the effects of peptides derived from the non-ACTH part of proopiomelanocortin (POMC), of met-enkephalin and of forskolin, alone or in combination with ACTH-(1-24), on the development of the ability of ovine fetal adrenal cells to produce both cAMP and corticosteroids in culture. N-POMC-(1-61) amide, gamma 2-melanocyte-stimulating hormone (MSH) and gamma 3-MSH behaved similarly in our system: 1) they increased slightly corticosterone (B) and cortisol (F) production without modification of cAMP output when added alone to the incubation medium, but this effect was observed only after 3 days in culture; 2) they potentiated the steroidogenic response to 10(-11) M ACTH-(1-24) but again only from Day 3 onwards; and 3) a 5-day treatment with the peptides induced fetal adrenal cell maturation resulting in the same enhancement of the B + F production stimulated by 10(-8) M ACTH-(1-24) without modification of the response in both cAMP and pregnenolone (P5). N-POMC-(1-80) and beta-lipotropic hormone (LPH) shared several common features in that, 1) the stimulation of B + F production by each of them alone was always significant and higher than that obtained with the other POMC-derived peptides [except ACTH-(1-24]; 2) they did not potentiate the steroidogenic action of 10(-11) M ACTH-(1-24); and 3) when cells were cultured in their presence for 5 days it resulted in an enhancement of the response to ACTH-(1-24), not only in B + F production but also in cAMP and P5 outputs. No effect of met-enkephalin was observed. The development of cAMP and B + F responses to ACTH-(1-24) provoked by forskolin was very close to that induced by the hormone itself, but forskolin, as opposed to ACTH-(1-24), was unable to induce a desensitization of the cAMP response. These data show that N-POMC-derived peptides can potentiate the acute steroidogenic activity of ACTH-(1-24) on ovine fetal adrenal cells after several days in culture. (+info)
Acute effects of mazindol on the secretion of ACTH, beta-lipotropin, beta-endorphin and cortisol in man.
(59/105)
The effects of mazindol, an anorexiant, on the secretion of anterior pituitary and adrenocortical hormones were examined in healthy male volunteers and in patients with Addison's disease. In healthy male volunteers, significant elevations in plasma ACTH, beta-endorphin, beta-lipotropin and growth hormone were induced by mazindol administration, though no changes were observed in plasma thyrotropin, luteinizing hormone, follicle-stimulating hormone or prolactin. Plasma ACTH increased in patients with Addison's disease, too. In addition, plasma cortisol increased, without a change in the plasma aldosterone levels after mazindol administration to normal subjects. (+info)
Biosynthesis of precursor corticotropin/endorphin-, corticotropin-, alpha-melanotropin-, beta-lipotropin-, and beta-endorphin-like material by cultured neonatal rat hypothalamic neurons.
(60/105)
Enzymatically dispersed hypothalamic cells derived from 15-day-old female rats were maintained in tissue culture for 4 days and then incubated for 2 hr in the presence of [35S]methionine. After such incubation, cell extracts contained multiple forms of 35S-labeled products that were specifically bound by immobilized affinity-purified antisera to corticotropin and beta-endorphin. Sequential use of these immobilized antisera revealed two molecular species (apparent Mr of 33,000 and 36,500) that contained both corticotropin and beta-endorphin antigenic determinants within the same molecule. Substances containing only one of these determinants were also present and co-eluted with corticotropin, alpha-melanotropin, beta-lipotropin, or beta-endorphin upon Sephadex G-50 gel filtration. Extracts of similarly labeled rat anterior and intermediate pituitary lobe cells contained two forms of the common precursor molecule corresponding to the same molecular weights estimated for the hypothalamic material and similar to it with respect to other physicochemical parameters. These data suggest that rat hypothalamus synthesizes corticotropin-related and beta-endorphin-related products via sequential cleavage of a larger common precursor molecule in a manner similar to the processing pathway demonstrated for the intermediate lobe of the pituitary. (+info)
Evidence for a signal sequence at the N terminus of the common precursor to adrenocorticothrophin and beta-lipotropin in mouse pituitary cells.
(61/105)
The precursor to corticotropin and beta-endorphin was synthesized in a reticulocyte cell-free system under the direction of mRNA from mouse AtT-20 pituitary tumor cells in the presence of [3H]proline, [3H]phenylalanine, [3H]leucine, [3H]valine, [3H]isoleucine or [35S]methionine. Automatic Edman degradation of the radioactive cell-free product showed the following N-terminal sequence: Pro-1, Met-2, Leu-11, Leu-12, Leu-13, Leu-15, Leu-16, Leu-17, Ile-21 and Val-23. The corticotropin-endorphin precursor was also labeled in AtT-20 cells with [3H]valine, [3H]leucine, [3H]tryptophan, [3H]serine, [35S]methionine or [35S]cysteine. Automatic Edman degradation of the radioactive intact cell form gave the following N-terminal sequence: Trp-1, Cys-2, Leu-3, Ser-5, Ser-6, Val-7, Cys-8, Leu-11, Leu-17, Leu-18 and tentatively Met-27. The sequence of the intact cell form from AtT-20 cells matches the sequence of the cell-free form of bovine pituitary precursor beginning at Trp-27, as determined by recombinant DNA technology [Nakanishi, S., Inoue, A., Kita, T., Nakamura, M., Chang, A. C. Y., Cohen, S. N., and Numa, S. (1979) Nature (Lond.) 278, 423-427]. The sequence of the mouse pituitary mRNA-directed cell-free translation product also matches the bovine precursor beginning at Pro-2. The results suggest that both the mouse and bovine precursors possess a signal sequence of 26 amino acids which is cleaved in intact cells. CNBr cleavage of [35S]cysteine-labelled intact cell precursor gave rise to an N-terminal fragment of a size compatible with the presence of a methionyl residue at or near position 27. (+info)
Detection and affinity purification of beta-endorphin precursors using a monoclonal antibody.
(62/105)
A monoclonal antibody to porcine beta-lipotropin has been produced which binds to the N-terminal (gamma-lipotropin) portion of the molecule. The antibody can be used to detect beta-lipotropin as well as other beta-endorphin precursors (predominantly a Mr 38 000 polypeptide) using radiobinding assay or the immunoblotting technique. Purification of the peptides can be readily achieved by affinity chromatography using the monoclonal antibody covalently bound to Sepharose 4B. As the antibody recognises the N-terminal part of beta-lipotropin, it can be used to detect and purify beta-lipotropin and other beta-endorphin precursors in the presence of beta-endorphin. (+info)
Complete structure of the porcine pro-opiomelanocortin mRNA derived from the nucleotide sequence of cloned cDNA.
(63/105)
Polyadenylated RNA isolated from porcine pituitary neurointermediate lobes was used to construct a cDNA library. The library was screened with a rat genomic DNA fragment specific for pro-opiomelanocortin sequences. Two positive clones, pJA-19 and pJA-20, containing respectively 850 bp and 550 bp were characterized. Sequence analysis of the cDNA inserts revealed the complete structure of the porcine pro-opiomelanocortin mRNA. This mRNA would include 129 5'-untranslated nucleotides, 801 nucleotides coding for the 267 amino acids precursor and 162 3'-untranslated nucleotides. Comparison with pro-opiomelanocortin mRNA sequences from other species shows regions of high homology not only in the coding sequences but also in the 5'untranslated region where the first 50 nucleotides are over 80% purines. (+info)
Silent corticotropic adenomas of the human pituitary gland: a histologic, immunocytologic, and ultrastructural study.
(64/105)
Among 300 surgically removed pituitary adenomas, 17 tumors containing immunoreactive 1-39 adrenocorticotropin (ACTH) and/or 19-39 ACTH, beta-lipotropin, and alpha-endorphin but unassociated with clinical signs of Cushing's disease have been detected. These neoplasms were divided into basophilic adenomas with strong periodic acid-Schiff (PAS) and lead-hematoxylin positivity and chromophobic tumors with moderate or no PAS and lead-hematoxylin positivity. The former were densely granulated tumors with a fine structure strikingly similar to that of functioning corticotropic cell adenomas. The latter were sparsely granulated with varying ultrastructural patterns. The marked morphologic diversity suggests that these adenomas, despite their similar immunocytologic characteristics, represent more than one entity. Clinically, the most common finding was a rapidly progressing visual defect. An unusually high incidence of infarction (5 cases) and recurrence (5 cases) was noted, underlining the importance of correct morphologic diagnosis and careful follow-up. (+info)