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PubMed1978

Sensitive new in vitro bioassay for melanocyte-stimulating activity using the skin of Anolis carolinensis.

An accurate, highly reproducible and sensitive bioassay for melanocyte-stimulating hormone (MSH) using the skin of Anolis carolinensis in vitro is described. The time taken for green Anolis skin fragments to change to a specific, visually assessed, green-brown color is dose-related, and this forms the basis of the new assay. The method is simple to perform, and 1 person may assay 20 samples in a day using the dorsal skin from a single adult lizard. The mean dose-response ranges between 48 X 10(-12) and 375 X 12(-12) M (38 to 625 pg/ml). Using the assay, alpha-MSH, beta-MSH, ACTH (4-10), and ACTH (1-10) were equipotent on a molar basis. For repeated bioassay of rat pituitary extracts, the dose-response curves were highly significant, and only 1 of the 9 pituitary dose-response curves deviated significantly from the slope of the standard alpha-MSH curve. The index of precision, lambda, for the 9 pituitary bioassays ranged between 0.037 and 0.081, while the mean 95% fiducial limits were -6.6 and 7.1% on either side of the estimated potency. The new rate method is compared with an earlier quantal method which also uses the isolated skin of Anolis carolinensis. The quantal method does not have dose-response characteristics and is therefore less accurate and reproducible than the new method; the coefficient of variation for repeated bioassay of the same pituitary extracts ranged from between 12 to 20% for the quantal method and between 2.9 to 5.7% for the new rate method.

Adrenocorticotropic Hormone↗

PubMed1976

Hormone-receptor interactions. The message sequence of alpha-melanotropin: demonstration of two active sites.

The purpose of this investigation was to elucidate the biological significance of lysine11 and of the tripeptide sequence =Lys-Pro-Val-NH2 for the biological activity of alpha-melanocyte-stimulating hormone. To this end the in vitro melanotropic activities of twenty-four synthetic peptides related to the hormone were determined. Extension or reduction of the length of the lysine11 side chain results in a marked decrease of the melanotropic potency of the respective analogue. The C-terminal tripeptide (11--13), the tetrapeptide (10--13), and the pentapeptide (9--13) were found to be hormonally active in the same order of magnitude as the central hexapeptide (5--10). The following conclusion was drawn: alpha-MSH possesses (in contrast to ACTH) two message sequences (active sites), (i)-Glu-His-Phe-Arg-Trp-, and (ii)-Gly-Lys-Pro-Val-NH2 which are capable of independently triggering the hormone receptor responsible for melanin dispersion. Thus, despite the close structural similarity of the two hormones, alpha-MSH and ACTH appear to react with their respective target cell receptors by quite different chemical mechanisms, implying different receptor structures.

Adrenocorticotropic Hormone↗

PubMed1975

Evidence that the pars intermedia and pars nervosa of the pituitary do not secrete functionally significant quantities of ACTH.

We have compared the capacity to secrete ACTH in response to stress or adrenalectomy in control rats and in those with total hypophysectomy (H), adenohypophysectomy (AH) with preservation of the intermediate and the neural lobes, neurohypophysectomy (NH) with removal of the pars nervosa and all or part of the pars intermedia with preservation of the adenohypophysis, or incomplete adenohypophysectomy (IAH) in which a portion of the adenohypophysis and all of the pars intermedia and pars nervosa were left intact. Plasma ACTH measured with an N-terminal antibody that reacts on an equimolar basis with ACTH and alpha-MSH but not with other known pituitary hormones was elevated after ether or tourniquet stress in all except the H group. Three weeks after adrenalectomy there was an elevated basal plasma ACTH and an augmented ACTH response to stress in intact and IAH but not in AH rats. When a more specific alpha11-24 ACTH antibody was used there was a high plasma ACTH after ether stress in the IAH, NH, and intact groups but not in the AH or H groups. Adrenal weight and plasma corticosterone after tourniquet or ether stress were indistinguishable in the AH and H groups and were much higher and nearly identical in the intact, NH and IAH groups. We conclude that only the adenohypophysis secretes functionally significant amounts of ACTH. Plasma ACTH detected by the N-terminal antibody in the AH group is probably related to alpha-MSH or similar peptides and is incapable of maintaining adrenal weight or stimulating corticosterone secretion.

Adrenal Glands↗

PubMed1976

Incorporation of 14C-labelled amino acids into corticotrophin-like intermediate lobe peptide and alpha-melanocyte-stimulating hormone by the rat pituitary neurointermediate lobe in vitro, and the identification of four new pars intermedia peptides.

At least seven radioactive peptides, which fractionated on Biogel P6, were found in rat neurointermediate lobes after incubation for 6 h with [14C]proline. Only three of these could be tentatively identified; one as alpha-melanocyte-stimulating hormone (alpha-MSH) and two as forms of corticotrophin-like intermediate lobe peptide (CLIP). One other cross-reacted partially with a beta-malanocyte-stimulating hormone (beta-MSH) antiserum, was acidically charged and eluted on Biogel P6 in roughly the same position as ACTH. The other three peptides showed no resemblance to alpha-MSH, CLIP, beta-MSH or ACTH.

Adrenocorticotropic Hormone↗

PubMed1977

[Immunofluorescence identification of cells with corticotropic and alpha-melanotropic activity in the hypophysis of the grass snake Natrix natrix L].

The use of anti ACTH (17-39) and alpha-MSH allowed us to detect by immunofluorescence in the Pituitary gland of Grass Snake the site of elaboration of ACTH and alpha-MSH. Corticotropic cells are located in the rostral part of the Pars Distalis and in the Pars intermedia. Melanotropic cells occupy the whole part of the Pars intermedia.

Adrenocorticotropic Hormone↗

PubMed1977

Induction of melanogenesis in the epidermal melanoblasts of newborn mouse skin by MSH.

The number of melanocytes positive to the dopa reaction in the epidermis was shown to increase after newborn mice were injected with alpha-MSH or DBc-AMP. The agents seemed to induce the initiation of melanogenesis in the pre-existing melanoblasts. Electron-microscopic observation also demonstrated that alpha-MSH induced not only maturation of melanosomes but also the formation of melanosomes.

Animals↗

PubMed1977

The effect of theophylline on the breakdown of the blood-aqueous barrier in the rabbit eye.

A disruption of the blood-aqueous barrier in rabbit eyes was elicited by topical prostaglandin E2, infrared irradiation of the iris, or subcutaneous alpha-melanocyte stimulating hormone (alpha-MSH). The course of the inflammatory reaction was followed by photoelectrical measurements of the aqueous flare in the anterior chamber. Pretreatment with intravenous theophylline, a phosphodiesterase inhibitor, significantly increased the protein leakage caused by prostaglandin E2 and alpha-MSH, but the response to infrared irradiation was slightly but not significantly enhanced. Intravenous theophylline given in higher doses caused per se an aqueous flare increase, which could not be inhibited by pretreatment with topical indomethacin. Our results indirectly indicate that accumulation of intraocular cAMP promotes a barrier damage and that cAMP might be the common effector of the barrier breakdown caused by prostaglandin as well as by nonprostaglandin agents.

Animals↗

PubMed1978

Immunocytological detection and localization of a peptide reacting with an alpha-endorphin antiserum in the corticotropic and melanotropic cells of the trout pituitary (Salmo irideus Gibb).

In the pituitary of the trout, the corticotropic and melanotropic cells display a strong immunocytological reaction with alpha-endorphin antiserum. This reaction persists even when alpha-endorphin antisera treated with beta-1-24ACTH or alpha-MSH are used. In the absence of pharmacological tests on the endorphic potencies of the compounds involved in the immunoreaction, it is not yeat clear whether this reaction is due to the presence of an alpha-endorphin-like peptide or simply an immunologically related peptide without the properties of endorphin. However, the presence of such peptides in the fish pituitary is interesting from the comparative point of view.

Adrenocorticotropic Hormone↗

PubMed1976

Hormonal influences of the extinction of conditioned taste aversion.

Conditioned taste aversion for a 5% glucose solution (sugar water) was induced in rats by an i.p. injection of LiCl 30 min after the first presentation of sugar water. Extinction of conditioned taste aversion was measured either in the forced-drinking test or in the preference-drinking test. In the forced-drinking test sugar water was the only fluid presented to the animals during extinction sessions. In the preference-drinking test the animals had the choice of tap water or sugar water. The rate of extinction was much slower in the preference test. The ACTH-analogues, ACTH 4-10 and ACTH 4-10 7d Phe, and alpha-MSH delayed extinction in the preference test but not extinction in the forced-drinking test. ACTH 11-24 was without any effect. MSH-release inhibiting factor (MIF) facilitated extinction in the forced-drinking test but did not alter extinction in the preference test. The peptides did not affect intake of tap water of preference of sugar water over tap water by control rats.

Adrenocorticotropic Hormone↗

PubMed1978

Steroidogenic activity of hACTH and related peptides on the human neocortex and fetal adrenal cortex in organ culture.

Explants prepared from the neocortex and the fetal zone of the human fetal adrenal (gestational age 13 to 18weeks) were maintained under conditions of organ culture for 7 to 9 days during which time they were exposed to hACTH and various related peptides. Corticotrophic activity was monitored by the daily release of dehydroepiandrosterone sulfate (3beta-hydroxy-5-androsten-17-one, 3-sulfate; DHA-S) and cortisol as quantified by radioimmunoassay, hACTH (2.2 x 10(-9) - 2.2 x 10(-8)M) was the most active in sustaining steroidogenesis by both neocortical and fetocortical cells. alpha-MSH possessed similar properties but not at concentrations lower than 10(-6)M, whereas CLIP (4.4 x 10(-9) - 1.1 x 10(-7)M), the 18-39 C-terminal moiety of ACTH, was devoid of activity. Corticotrophic activity with respect to fetocortical explants appeared to be that of maintenance of function best illustrated by dehydroepiandrosterone sulfate biosynthesis, while enhancement of steroidogenesis was observed in the neocortex as manifested by cortisol release. Although not eliminating the possible existence of a specific fetal corticotrophin related to ACTH1-39, the data indicate that hACTH is capable of regulating steroidogenesis in the fetal zone which is primarily geared to the formation of dehydroepiandrosterone sulfate.

Adrenal Cortex↗

PubMed1976

Possible association of increased rat behavioral effects and increased striatal dopamine and norepinephrine levels during the DOPA-potentiation test.

Previous reports have indicated that alpha-MSH release inhibiting hormone (MIF-1) increased the behavior occurring as a result of the dihydroxyphenylalanine (DOPA) potentiation test [3,7]. This study was undertaken to see whether dopamine (DA) or norepinephrine (NE) levels likewise increased in the test animals. The DOPA potentiation test was performed as follows: 2-4 hr before behavior measurement, 40 mg/kg of the monoamine oxidase inhibitor pargyline HCl was given orally. Two hr later this was followed by the intraperitoneal (IP) injection of MIF-1 at doses of 0.1, 0.3 or 1.0 mg/kg. Behavioral measurement was begun after the IP injection of 200 mg/kg of dl-DOPA 1-2 hr after the MIF-1. The parameters included social interaction, aggressiveness, fighting, ataxia, jumping, defecation, urination and salivation. The animals were beheaded while the behavior was still increased and the striatal area removed, placed in aluminum foil, and kept at -50 degrees C until assayed. In general, especially among the younger animals, a significant correlation (p=0.05 to p=0.01) was found between the increased behavioral responses to MIF-I and the rise in DA. Because of a few exceptions to this correlation the possibility is suggested that MIF-I might also affect behavior by acting directly on the postsynaptic membrane thus bypassing any change in NE or DA which is known to increase cycli AMP in the striatum.

Animals↗

PubMed1976

Neurochemical responses of mice to ACTH and lysine vasopressin.

Subcutaneous administration of ACTH 1-24 to mice increased the incorporation of [3H]lysine into brain and liver proteins, an effect which resembled that due to footshock. Corticosterone administration did not mimic these effects. ACTH 4-10 increased the [3H]lysine incorporation into brain or liver. These results are consistent with ACTH mediating the effects of footshock. However, dexamethasone decreased the brain responses to both footshock and ACTH, but while the liver response to ACTH was blocked, the footshock response was only diminished. This suggests a neural component in the response of the liver and possibly the brain. Intraventricular administration of ACTH 1-24 or ACTH 4-10 (D-phe), but not ACTH 4-10, increased [3H]lysine incorporation into brain protein. These neurochemical responses parallelled a distinctive pattern of behavior characterized by stretching, yawning and excessive grooming. Treatment for 3 days with long-acting preparations of ACTH 4-10, ACTH 4-10 (D-phe) or ACTH 1-24 increased the conversion of [3H]tyrosine into dopamine but not norepinephrine, alpha-MSH, beta-MSH or LVP had no such effect. Similar treatment with ACTH 4-10 or ACTH 1-24 increased striatal tyrosine hydroxylase activity measured in vitro, but did not significantly alter the enzyme activity from other brain regions. We conclude that ACTH peptides can stimulate protein and dopamine metabolism in mouse brain and that LVP has no such effects.

Adrenocorticotropic Hormone↗

PubMedDate not supplied

Subcellular localization of immunoreactive alpha-melanocyte stimulating hormone in human brain.

The regional and subcellular distribution of immunoreactive alpha-melanocyte stimulating hormone (alpha-MSHi) in the post mortem adult human brain was investigated. alpha-MSHi was highly concentrated in medial basal hypothalamic tissue (1.02 ng/mg protein). Lower levels of alpha-MSHi were present in the optic chiasm and mammillary bodies, 0.08 and 0.11 ng/mg protein, respectively. The concentrations of alpha-MSHi in cerebellum and frontal cerebral cortex were 1/1,000th that of the medial basal hypothalamus. When medial basal hypothalamic homogenates were subjected to discontinuous or continuous sucrose density gradients, alpha-MSHi was found to be associated primarily with subcellular particles which resembled isolated nerve terminals, i.e., synaptosomes. Low to undetectable amounts of alpha-MSHi were found in the cytosol or the myelin/microsome fraction of the gradients. The results of these studies are consistent with the view that alpha-MSH is a neuronal peptide in the human brain.

Brain↗

PubMed1976

Stimulation of growth hormone release by luteinizing hormone-releasing hormone and melanocyte-stimulating hormone-release inhibiting hormone in the hypophysectomized rat bearing an ectopic pituitary.

Intrajugular administration of LHRH (0-6 and 1-2 mug) in hypophysectomized rats which received renal grafts of anterior pituitary induced a small but significant rise in plasma GH 5 and 10 min post-treatment. LHRH, at the same dose levels, was ineffective in weight-matched intact controls. MIF, at the dose of 1-2 mug, induced a slight GH rise 5 min after treatment in hypophysectomized trasnplanted rats, while it was ineffective in intact controls. Unlike the two hypothalamic peptides, alpha-MSH (0-6 and 1-2 mug) was ineffective as a GH-releaser in both transplanted and intact rats.

Animals↗

PubMed1975

A sensitive bioassay for the determination of human plasma ACTH levels.

A sensitive bioassay for the measurement of plasma ACTH is presented. The use of silicic acid adsorption of plasma, with a subsequent acid wash and aqueous acetone desorption, was successful in removing those substances which had interfered with the steroidogenic response of dispersed adrenal cells when unextracted plasma was employed. This extraction procedure extracted 72-76% of ACTH present in plasma. Two pg ACTH1-39 could be consistently detected. Alpha-hACTH1-39 and alpha-pACTH1-39 exhibited equal potencies. Beta-MSH was ineffective at dosage levels up to 2 x 10(8) pg. One x 10(8) pg of ACTH1-10, ACTH4-10, or alpha-MSH had a steroidogenic effect equivalent to that of 40 pg ACTH1-39. ACTH 17-39 and ACTH 11-24 were incapable of stimulating steroid production at doses of 1 x 10(8) pg. Excesses of the latter, but not of the former appeared to be able to antagonize the steroidogenic effect of ACTH1-39. Plasma from normal subjects, bioassayed by this extraction procedure, contained 12-186 pg/ml ACTH at 0400-0800: 14-93 pg/ml ACTH at 1000-1300, and less than 10-34 pg/ml ACTH at 1600-2200. Hypoglycemia and vasopressin administration were followed by increases in plasma ACTH concentratrations. Plasma ACTH concentrations in untreated patients with Cushing's disease (sampled over the period 0900-1300) ranged from 65-220 pg/ml. Three patients with Addison's disease (untreated or 12 h following replacement steroid withdrawal) had ACTH concentrations of 223, 370 and 1226 pg/ml. Markedly elevated ACTH concentrations were observed in a patient with Nelson's syndrome (391 and 835 pg/ml). Bioassayable ACTH was not detected in 2 patients with panhypopituitarism.

Acetone↗

PubMed1976

[Cyto-immunological study of the Pleurodele pituitary gland].

In the pituitary of an Amphibian (Urodela), various cell types were localized by cytoimmunological techniques: corticotrophs located in a rostral zone near the median eminence, ventral orangeophilic cells secreting a prolactin-like hormone and erythrosinophilic cells in a more dorso-caudal situation secreting growth hormone. Alpha-MSH and beta-MSH produceng cell were identified in the intermediate lobe; these cells were also labelled with antibodies against 1-24 ACTH and 17-39 ACTH. These data are in accordance with results obtained after an experimental study of the prolactin cells.

Adrenocorticotropic Hormone↗

PubMed1977

[Demonstration by immunofluorescence of adenohyphysis corticotropin and melanotropin cells in Erythrocebus patas, Cercopithecus aethiops and Papio hamadryas].

Using antibodies against synthetic corticotropic hormones (1-24 ACTH and 17-39 ACTH), and melanotropic hormones (alpha-MSH and beta-MSH), it is possible to identify corticotropic and melanotropic cells in the adenohypophysis of three species of monkeys : Erythrocebus patas, Cercopithecus aethiops and Papio hamadryas. The corticotropic cells are numerous in the anterior lobe in both the adult and infant male and female monkeys of these three species. The intermediate lobe reacts with antibodies against ACTH and also with antibodies against the two MSH. In the anterior lobe, the corticotropic cells react also with anti-beta MSH antibody but not with the anti-alpha MSH antibody.

Adrenocorticotropic Hormone↗

PubMed1978

Mechanism of alpha-melanotropin action.

A structure-function study of alpha-melanotropin has shown that this tridecapeptide consists of two message sequences, (-Glu)-His-Phe-Arg-Trp- and -Gly-Lys-Pro-Val-NH2, and a potentiator sequence, Ac.Ser-Tyr-Ser-Met-(Glu-), when acting on its melanophore receptors. The key elements of the message, -Phe-Arg- and -Lys-Pro-, do not correspond exactly to those responsible for eliciting the effect in other tissues. It appears that alpha-MSH contains more information than would be necessary to interact with only one complementary receptor site; therefore, the topography of the hormone exposed to the binding site may be different on contact with the receptors of different target cells. To further investigate this aspect, new methods for the isolation and characterization of functional receptors must be developed. We are investigating the use of chemically well-defined, biologically active, covalent hormone-macromolecule complexes for this purpose. Another approach utilizes model receptors with a recognition pattern similar to that of the biological receptor, as described in this communication for certain highly specific antibodies.

Amino Acid Sequence↗