Different Effects of K&lt;sup&gt;+&lt;/sup&gt; and Ca&lt;sup&gt;++&lt;/sup&gt; on &lt;i&gt;α&lt;/i&gt;-MSH and ACTH Release from Superfused Neurointermediate Lobe of the Rat Hypophysis

Schmitt, Gisela; Briaud, B.; Mialhe, C; Stutinsky, F

doi:10.1159/000122875

Cited by 29 publications

(13 citation statements)

References 13 publications

(14 reference statements)

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“…Indeed, instead of sti mulating hormonal release as a result of depolarizing of the cellular membrane, high K+, on the contrary, appears to in hibit release of a-MSH and (3-endorphin [23,33,36). Tilders et al [33] have demonstrated that in the rat, this effect is caused by DA release from nerve endings at the levels of the IL which, in turn, inhibits a-MSH secretion.…”

Section: Discussionmentioning

confidence: 99%

“…Two perifusion chambers, containing 40-50 NIL (from I-day-old mice), 25-30 NIL (from 7-day-old mice), or 10 NIL (from adults), were perifused with the aid of a constant flow (2 m l/ 10 min) of Krebs-Ringer (KR) bicarbonate buffer as we have previ ously described [23]. When the K* concentration was enhanced from 5.95 to 47.5 pM (8 K*), the concentration of NaCI was adjust ed to maintain iso-osmotic conditions.…”

Section: Superfusion Methodsmentioning

confidence: 99%

“…NIL a-MSH contents were measured using a radioimmunoas say (RI A ), according to a method previously described [23]. As seen in figure I, serial dilutions of NIL extracts generated displacement curves parallel to that obtained with synthetic a-MSH.…”

Section: A-m Sh Radioimmunoassaysmentioning

confidence: 99%

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Evidence for a Possible Dopaminergic Control of Pituitary Alpha-MSH during Ontogenesis in Mice

Schmitt¹,

Stoeckel²,

Koch³

1981

Neuroendocrinology

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This study was aimed at determining the α-MSH and ACTH contents of the neurointermediate lobe (NIL) of the mouse hypophysis during ontogenesis, as well as the ability of the gland, incubated in a perfusion system, to respond to dopamine (DA) and high potassium (K⁺). We showed that: (1) the NIL content of α-MSH exhibited a biphasic pattern of evolution, characterized by a dramatic increase appearing between postnatal days 3 and 5. By contrast, NIL ACTH content followed a completely different pattern of evolution; (2) both DA and high K⁺ reversibly inhibited MSH release from superfused NIL, the latter effect being more pronounced with the use of pituitaries from 7-day-old than from 1-day-old mice; (3) the inhibitory influence of high K⁺ was impaired by haloperidol pretreatment. From these data, as well as from morphological observations, it appears that functional DA receptors seem to be present on melanotrophs of the developing hypophysis in mice and that the increase in α-MSH in IL cells observed shortly after birth may result from the onset of inhibitory influence exerted by dopaminergic innervation on hormonal secretion. This view, however, does not preclude possible effects of other hypothalamic releasing and/or inhibiting factors.

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Section: Discussionmentioning

confidence: 99%

Section: Superfusion Methodsmentioning

confidence: 99%

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Evidence for a Possible Dopaminergic Control of Pituitary Alpha-MSH during Ontogenesis in Mice

Schmitt¹,

Stoeckel²,

Koch³

1981

Neuroendocrinology

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“…Indeed, it has recently been shown that 45 mM-K stimulates the co-ordinated release of several melanotroph products, including melanocyte-stimulating hormone (Jackson et al 1981). Earlier studies on hormone release had shown no stimulatory effect ofexcess K, possibly because the preparations used contained inhibitory nerve endings (Schmitt, Briaud, Mialhe & Stutinsky, 1979;Tilders, van der Weude, Swaab & Mulder, 1979). In addition, if hormone release depends on the activation ofpotential-dependentCa channels which rapidly inactivate, the duration of the response will be limited; such may have been the explanation for the failure of Bower & Hadley (1972) to detect stimulation of mouse melanotrophs.…”

Section: Stimulation Of [3h]methyltriphenylphosphonium Ion Efflux By mentioning

confidence: 99%

Stimulation of calcium‐dependent release of labelled protein from pulse‐labelled mouse pituitary intermediate lobe tissue

Thornton

1982

The Journal of Physiology

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However, recovery also occurred during maintained depolarization provided the Ca concentration was reduced sufficiently. Recovery was complete at 0 4 mM-Ca or less, and at higher concentrations the extent of recovery depended on the Ca concentration selected.6. It is concluded that depolarization opened potential-dependent Ca channels.permitting Ca entry and causing the release of labelled products. The response was brief probably because the Ca channels were inactivated. Since the channels were not inactivated by depolarization in low Ca, inactivation may result from Ca entry.

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“…Tilders [30] and Tilders et al [33] reported a time dependency of the ratio of Received: November 3,1982 Accepted after revision: March 14, 1983 aMSH immunoactivity to ACTH bioactivity released from perifused neurointermediate lobes (NI) and differential stimulation by /-isoproterenol of species of ACTH bioactiv ity and ACTH, aMSH and |3END immunoactivity. Fur thermore, elevated K* concentration inhibits the release of aMSH but stimulates the release of ACTH bioactivity [21,23,26, 30]. Mains and Eipper [ 16] showed that /-isoproteren ol causes the release from pituitary tumor cells of aMSH, yLPH and N-terminal immunoactive peptides that are not released under basal conditions.…”

mentioning

confidence: 99%

Differential Control of the Release of Pro-Opiomelanocortin-Derived Peptides from the Pars intermedia of the Rat Pituitary

Randle¹,

Moor²,

Kraicer³

1983

Neuroendocrinology

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The pars intermedia (PI) of the adenohypophysis synthesizes pro-opiomelanocortin, which, through post-translational processing, gives rise to a group of chemically related peptides, including αMSH, ACTH, CLIP, LPHs and endorphins. We investigated the control of release of these peptides using an in vitro system. We perifused either acutely dispersed rat PI cells or intact neurointermediate lobes (NI). Perifusion medium and cell extracts were subjected to a series of bioassays (BA) and radioimmunoassays (RIA) (including MSH-BA, αMSH-RIA, ACTH-BA, ACTH-RIA, LPH-RIA) and a receptor-binding assay for morphine-like activity (MLA). The relative amounts of release of the various peptide activities was examined under basal and stimulated conditions. Under basal conditions, intact NI released approximately equal amounts of αMSH immunoactivity, MSH bioactivity and MLA, slightly less ACTH and LPH immunoactivity and far less ACTH bioactivity. Relative to αMSH immunoactivity, the rate of release of ACTH bioactivity decreased in the course of an experiment while the release of the other peptide activities increased. The peptide activities were released from dispersed PI cells in relative amounts similar to those from intact NI. The relative amounts of peptide activities contained in extracts of dispersed PI cells differed from the amounts released such that when compared to αMSH immunoactivity, the release of LPH and ACTH immunoactivities and MLA is 3–4 times greater while the release of ACTH bioactivity is one-half. Serotonin (10^–7–10^–5M) markedly stimulated the release of ACTH bioactivity from both dispersed PI cells and intact NI in a dose-related manner. Serotonin had a smaller stimulatory effect on the release of αMSH and LPH immunoactivity but had no effect on the release of MLA and ACTH immunoactivity. These observations indicate that there is differential control of the release of POMC-derived peptides from the rat PI.

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Different Effects of K<sup>+</sup> and Ca<sup>++</sup> on <i>α</i>-MSH and ACTH Release from Superfused Neurointermediate Lobe of the Rat Hypophysis

Cited by 29 publications

References 13 publications

Evidence for a Possible Dopaminergic Control of Pituitary Alpha-MSH during Ontogenesis in Mice

Evidence for a Possible Dopaminergic Control of Pituitary Alpha-MSH during Ontogenesis in Mice

Stimulation of calcium‐dependent release of labelled protein from pulse‐labelled mouse pituitary intermediate lobe tissue

Differential Control of the Release of Pro-Opiomelanocortin-Derived Peptides from the Pars intermedia of the Rat Pituitary

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