The blocking effect of magnesium on the secretion of adrenal catecholamines induced by the omission of sodium from the extracellular medium.
The blocking action of Mg++ on catecholamine release induced by the substitution of extracellular Na+ by an osmotic equivalent amount of sucrose was studied in isolated, perfused bovine adrenal glands. Perfusing glands with 10 mM Mg++ produced at 51.1% inhibition on catecholamine release evoked by Na+ omission. Increasing the concentration of Mg++ to 20 mM this inhibitory effect was enhanced to 90.3%. D-600 (0.3 mM) promoted a marked blockade of acetylcholine-induced release of catechol hormones that was partially and significantly reverted increasing the concentration of Ca++ in the perfusion medium. D-600 (0.3 mM) failed to inhibit the catecholamine-releasing effect of Na+ deprivation. In adrenal glands previously perfused with D-600 (0.3 mM) and then exposed to a Locke solution containing D-600 (0.3 mM) + Mg++ (10 or 20 mM) the inhibition of the secretory responses evoked by the omission of Na+ was of the same magnitude as that obtained when the glands were perfused with Mg++ (10 or 20 mM) in the absence of D-600. These results are compatible with the view that the blocking effect of Mg++ may involve an intracellular site of action and that the access of Mg++ into the chromaffin cell may not be mediated through the Ca++ channels.
D000109:Acetylcholine / Q000494:pharmacology; D000311:Adrenal Glands / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002395:Catecholamines / Q000378:metabolism*; D002417:Cattle; D005711:Gallopamil / Q000494:pharmacology; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology*; D010477:Perfusion; D012964:Sodium / Q000494:pharmacology*
D002395:Catecholamines; D005711:Gallopamil; D012964:Sodium; D008274:Magnesium; D000109:Acetylcholine; D002118:Calcium