Sodium Inhibits Hormone Release and Stimulates Calcium Efflux from Isolated Nerve Endings of the Rat Neurohypophysis

Overview

Journal Cell Mol Neurobiol

Publisher Springer

Specialties Cell Biology
Molecular Biology
Neurology

Date 1991 Jun 1

PMID 1868507

Authors

K Payza

J T Russell

Affiliations

Soon will be listed here.

Abstract

1. We studied the effects of extracellular sodium on the secretion of vasopressin (VP) and oxytocin (OT) and the efflux of 45Ca from isolated, perfused nerve endings of the rat neurohypophysis (neurosecretosomes). 2. Upon removal of sodium from the perfusing medium, basal release of VP and OT increased by 3.95 +/- 0.23- and 3.71 +/- 0.22-fold, respectively, followed by a decline to about double the levels in normal (150 mM) sodium (P less than or equal to 0.1). 3. Compared to neurosecretosomes perfused in normal (150 mM) sodium, omission of sodium from the medium augmented ionomycin-induced VP and OT secretion by 66 +/- 5- and 20 +/- 3-fold, respectively, and A23187-induced secretion was increased 1.3 +/- 0.4- and 1.3 +/- 0.1-fold (P less than or equal to 0.01 for both ionophores). 4. The inhibition of ionomycin-induced secretion by sodium was concentration dependent (P less than or equal to 0.01 for sodium greater than or equal to 5 mM); the IC50 was about 10 mM sodium for both hormones, and the Hill slope was close to -1. 5. The rate of 45Ca efflux from neurosecretosomes showed 2.7 +/- 0.1-fold stimulation upon increasing sodium from 4.5 to 150 mM (P less than or equal to 0.01). 6. Our results suggest that sodium inhibits basal and stimulated secretion at the nerve terminal, possibly by reducing intraterminal calcium through sodium/calcium exchange.

References

Cazalis M, Dayanithi G, Nordmann J . Hormone release from isolated nerve endings of the rat neurohypophysis. J Physiol. 1987; 390:55-70. PMC: 1192166. DOI: 10.1113/jphysiol.1987.sp016686. View

Miledi R . Transmitter release induced by injection of calcium ions into nerve terminals. Proc R Soc Lond B Biol Sci. 1973; 183(1073):421-5. DOI: 10.1098/rspb.1973.0026. View

Nordmann J, Dayanithi G, Lemos J . Isolated neurosecretory nerve endings as a tool for studying the mechanism of stimulus-secretion coupling. Biosci Rep. 1987; 7(5):411-26. DOI: 10.1007/BF01362504. View

Sanchez-Armass S, Blaustein M . Role of sodium-calcium exchange in regulation of intracellular calcium in nerve terminals. Am J Physiol. 1987; 252(6 Pt 1):C595-603. DOI: 10.1152/ajpcell.1987.252.6.C595. View

Pocotte S, Frye R, Senter R, Terbush D, Lee S, Holz R . Effects of phorbol ester on catecholamine secretion and protein phosphorylation in adrenal medullary cell cultures. Proc Natl Acad Sci U S A. 1985; 82(3):930-4. PMC: 397161. DOI: 10.1073/pnas.82.3.930. View

Payza K, Russell J . Activation and inactivation of oxytocin and vasopressin release from isolated nerve endings (neurosecretosomes) of the rat neurohypophysis. J Neurochem. 1991; 57(2):499-508. DOI: 10.1111/j.1471-4159.1991.tb03779.x. View

Blanco P, Martinez-Serrano A, Bogonez E, Satrustegui J . Effect of Quin-2 on 45Ca2+ uptake mediated by Na+i/Ca2+o exchange and 45Ca2+ efflux in rat brain synaptosomes: a requirement for [Ca2+]i. Cell Calcium. 1990; 11(1):25-33. DOI: 10.1016/0143-4160(90)90046-w. View

DiPolo R, Beauge L . Asymmetrical properties of the Na-Ca exchanger in voltage-clamped, internally dialyzed squid axons under symmetrical ionic conditions. J Gen Physiol. 1990; 95(5):819-35. PMC: 2216346. DOI: 10.1085/jgp.95.5.819. View

Dreifuss J, Grau J, Bianchi R . Antagonism between Ca and Na ions at neurohypophysial nerve terminals. Experientia. 1971; 27(11):1295-6. DOI: 10.1007/BF02136696. View

10.

Blaustein M . Calcium transport and buffering in neurons. Trends Neurosci. 1988; 11(10):438-43. DOI: 10.1016/0166-2236(88)90195-6. View

11.

Nordmann J . Evidence for calcium inactivation during hormone release in the rat neurohypophysis. J Exp Biol. 1976; 65(3):669-83. DOI: 10.1242/jeb.65.3.669. View

12.

Mattson M, Guthrie P, Kater S . A role for Na+-dependent Ca2+ extrusion in protection against neuronal excitotoxicity. FASEB J. 1989; 3(13):2519-26. DOI: 10.1096/fasebj.3.13.2572500. View

13.

Cazalis M, Dayanithi G, Nordmann J . Requirements for hormone release from permeabilized nerve endings isolated from the rat neurohypophysis. J Physiol. 1987; 390:71-91. PMC: 1192167. DOI: 10.1113/jphysiol.1987.sp016687. View

14.

Chandler L, Crews F . Calcium- versus G protein-mediated phosphoinositide. Hydrolysis in rat cerebral cortical synaptoneurosomes. J Neurochem. 1990; 55(3):1022-30. DOI: 10.1111/j.1471-4159.1990.tb04592.x. View

15.

Nordmann J, Zyzek E . Calcium efflux from the rat neurohypophysis. J Physiol. 1982; 325:281-99. PMC: 1251394. DOI: 10.1113/jphysiol.1982.sp014150. View

16.

DiPolo R, Beauge L, Rojas H . In dialyzed squid axons Ca2+i activates Ca2+o-Na+i and Na+o-Na+i exchanges in the absence of Ca chelating agents. Biochim Biophys Acta. 1989; 978(2):328-32. DOI: 10.1016/0005-2736(89)90132-6. View

17.

Robinson I, Russell J, THORN N . Calcium and stimulus secretion coupling in the neurohypophysis. V. The effects of the Ca2+ ionophores A23187 and X537 A on vasopressin release and 45Ca2+ efflux; interactions with sodium and a verapamil analogue (D600). Acta Endocrinol (Copenh). 1976; 83(1):36-49. View

18.

Lastowecka A, TRIFARO J . The effect of sodium and calcium ions on the release of catecholamines from the adrenal medulla: sodium deprivation induces release by exocytosis in the absence of extracellular calcium. J Physiol. 1974; 236(3):681-705. PMC: 1350857. DOI: 10.1113/jphysiol.1974.sp010460. View

19.

Smith S, Augustine G . Calcium ions, active zones and synaptic transmitter release. Trends Neurosci. 1988; 11(10):458-64. DOI: 10.1016/0166-2236(88)90199-3. View

20.

Muller J, THORN N, Torp-Pedersen C . Effects of calcium and sodium on vasopressin release in vitro induced by a prolonged potassium stimulation. Acta Endocrinol (Copenh). 1975; 79(1):51-9. DOI: 10.1530/acta.0.0790051. View