Potassium-modulated secretion of immunoreactive melanocyte-stimulating hormone and endorphin from mouse neuro-intermediate lobes

Evidence for stimulus-secretion uncoupling and rate sensitivity

L. D. Keith, R. G. Allen, J. Stack, L. M. Robertson, John Kendall

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

A multi-chamber perifusion system, capable of detecting transient secretory events, was used to define the roles of stepwise changes and gradients of K+ concentration in modulation of α-MSH and endorphin secretion. Fifteen dispersed mouse neuro-intermediate lobes per chamber were perifused with Dulbecco's Modified Eagle Medium at 0.5 ml/min. One-min fractions were collected. Ten min of 67 mM K+ elicited an immediate, very brief 4-fold increase in secretion of both hormones. Surprisingly, the return to normal K+ elicited a similar increase in secretion. Ten min K+-free medium produced an immediate decrease in secretion. Exposure to a 10-min 0-67 mM K+ gradient did not produce an increase in secretion; however, the stepwise return to normal K+, identical to that in the first experiment, elicited an immediate, brief increase in secretion. Conclusions: 1) The rapid decline in secretory activity during 67 mM K+ cannot be explained either by 'down regulation' of receptors, since this secretagogue is not receptor-mediated, or by depletion of labile hormone, since a second secretory episode occurred immediately following termination of high K+. This suggests that some other cellular mechanism 'uncouples' stimulus-secretory mechanisms. 2) Although depolarization with high K+ and hyperpolarization with K+-free medium were associated with increases and decreases, respectively, in secretion, it appears that it is the rate of ion flux rather than polarization which is responsible for stimulus-secretion coupling.

Original languageEnglish (US)
Pages (from-to)1886-1888
Number of pages3
JournalEndocrinology
Volume112
Issue number5
StatePublished - 1983

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Endorphins
Melanocyte-Stimulating Hormones
Potassium
Hormones
Eagles
Down-Regulation
Ions

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

Cite this

Potassium-modulated secretion of immunoreactive melanocyte-stimulating hormone and endorphin from mouse neuro-intermediate lobes : Evidence for stimulus-secretion uncoupling and rate sensitivity. / Keith, L. D.; Allen, R. G.; Stack, J.; Robertson, L. M.; Kendall, John.

In: Endocrinology, Vol. 112, No. 5, 1983, p. 1886-1888.

Research output: Contribution to journalArticle

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abstract = "A multi-chamber perifusion system, capable of detecting transient secretory events, was used to define the roles of stepwise changes and gradients of K+ concentration in modulation of α-MSH and endorphin secretion. Fifteen dispersed mouse neuro-intermediate lobes per chamber were perifused with Dulbecco's Modified Eagle Medium at 0.5 ml/min. One-min fractions were collected. Ten min of 67 mM K+ elicited an immediate, very brief 4-fold increase in secretion of both hormones. Surprisingly, the return to normal K+ elicited a similar increase in secretion. Ten min K+-free medium produced an immediate decrease in secretion. Exposure to a 10-min 0-67 mM K+ gradient did not produce an increase in secretion; however, the stepwise return to normal K+, identical to that in the first experiment, elicited an immediate, brief increase in secretion. Conclusions: 1) The rapid decline in secretory activity during 67 mM K+ cannot be explained either by 'down regulation' of receptors, since this secretagogue is not receptor-mediated, or by depletion of labile hormone, since a second secretory episode occurred immediately following termination of high K+. This suggests that some other cellular mechanism 'uncouples' stimulus-secretory mechanisms. 2) Although depolarization with high K+ and hyperpolarization with K+-free medium were associated with increases and decreases, respectively, in secretion, it appears that it is the rate of ion flux rather than polarization which is responsible for stimulus-secretion coupling.",
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