Secretagogue effect of barium on output of melanocyte-stimulating hormone from pars intermedia of the mouse pituitary.
- 1 May 1983
- journal article
- research article
- Published by Wiley in The Journal of Physiology
- Vol. 338 (1), 243-257
- https://doi.org/10.1113/jphysiol.1983.sp014671
Abstract
Ba ions caused an intense and prolonged discharge of MSH from perifused neurointermediate lobes of mouse pituitaries and dispersed pars intermedia cells. The effect persisted in chronically cultured lobes or cells. It did not require Ca, but, like the Ca-dependent response to excess K, was blocked by cyanide combined with glucose lack. The secretogogue effect of Ba was blocked or prevented by Co or by excess Ca, both of which can reduce inward Ba currents through Ca channels. Prior exposure to excess K partially reduced the secretagogue effect of Ba, suggesting that depolarization caused some inactivation of Ba current. Excess K elicited secretion that was transient, and prior exposure of preparations to excess K (in the absence of Ca) profoundly suppressed the secretagogue effect of Ca. The evidence is consistent with the view that inward Ca current rapidly inactivates in these cells. It is concluded that Ba ions have a potent and persistent direct secretagogue effect on the melanotrophs that may reflect, in part, their ability to penetrate Ca channels more easily than Ca ions. The strong secretagogue effects of Ba on melanotrophs may be of considerable utility in studies on MSH secretion since a physiological secretagogue has yet to be discovered. Moreover, since the responses of melanotrophs (and other endocrine cells) to Ba can be distinguished from those of various other secretory cells and neurones, it is suggested that Ba may provide a tool for characterizing the distinctive membrane properties of the Ba-responsive endocrine cells.This publication has 56 references indexed in Scilit:
- Calcium transport mechanisms in membrane vesicles from guinea pig brain synaptosomes.Journal of Biological Chemistry, 1981
- Calcium component to action potentials in rat pars intermedia cells.The Journal of Physiology, 1980
- THE REGULATION OF INTRACELLULAR CALCIUM IN PRESYNAPTIC NERVE TERMINALS*Annals of the New York Academy of Sciences, 1978
- On the role of barium in supporting the asynchronous release of acetylcholine quanta by motor nerve impulses.The Journal of Physiology, 1978
- Effects of internal and external cations and of ATP on sodium-calcium and calcium-calcium exchange in squid axonsBiophysical Journal, 1977
- The significance of melanocyte-stimulating hormone (MSH) and the control of its secretion in the mammal.1977
- The role of the alkaline earth ions in anaphylactic histamine secretionThe Journal of Physiology, 1972
- Divalent Cations and the Blood Platelet Release ReactionNature New Biology, 1972
- Energy Dependent Bivalent Cation Translocation in Rat Liver MitochondriaEuropean Journal of Biochemistry, 1970
- The role of calcium in the secretory response of the adrenal medulla to acetylcholineThe Journal of Physiology, 1961