Activation of Na⁺/Mg²⁺ antiport in thymocytes by cAMP

Abstract

Mg2+ efflux from Mg2+‐loaded rat thymocytes was stimulated by 0.1 mM dibutyryl cAMP (db cAMP). The activation of Mg2+ efflux by db cAMP was more expressed at lower Mg2+‐loading, cAMP induced only a very small increase in the concentration of intracellular free Mg2+ which cannot explain the activation of Na+/Mg2+ antiport. From these results it was concluded that cAMP increases the affinity of the Na+/Mg2+ antiporter for intracellular Mg2+, probably by phosphorylation.

Activation of the Na + -H + Exchanger Modulates Angiotensin II–Stimulated Na + -Dependent Mg 2+ Transport in Vascular Smooth Muscle Cells in Genetic Hypertension

“…Although quinidine is not a selective blocker of the Na ϩ -Mg 2ϩ exchanger, it has been extensively used to study this transporter in various cell types. 12,14,16,17,21,40 Effects of quinidine appear to be independent of Ca 2ϩ transporters, because quinidine did nor alter [Ca 2ϩ ] i in VSMCs from WKY or SHR (data not shown). In Na ϩ -free conditions and in the presence of quinidine, Ang II-stimulated [Mg 2ϩ ] i responses were inhibited, indicating that the Na ϩ -Mg 2ϩ exchanger plays a major regulatory role in Mg 2ϩ transport and that in SHR it may contribute to altered intracellular Mg 2ϩ homeostasis in both the basal and stimulated states.…”

Increased activity of the Mg2+/Na+ exchanger in red blood cells from essential hypertensive patients.

“…This mechanism was recently described by Feray and Gara y28-3o j n human and rat erythrocytes. Evidence for a Mg 2+ /Na + exchanger has been obtained in giant squid axon, 31 and the existence of a similar mechanism in liver cells, 32 thymocytes, 33 and myocardiocytes has been suggested. 34 On the basis of these considerations, the aim of the present study was to detect possible abnormalities of the Na + -dependent Mg 2+ efflux (the Mg 2+ /Na + exchanger) in erythrocytes from essential hypertensive patients.…”

Angiotensin II Type I Receptor Modulates Intracellular Free Mg2+ in Renally Derived Cells via Na+-dependent Ca2+-independent Mechanisms

“…The Na ϩ / Mg 2ϩ exchanger was first demonstrated in the squid giant axon where Na ϩ entry is coupled to Mg 2ϩ moving out of the cell (14). Na ϩ -dependent Mg 2ϩ transport is inhibited by amiloride, quinidine, imipramine, and manganese, and it may be regulated by cAMP, protein kinase C, and the Na ϩ /H ϩ antiporter (15)(16)(17)(18)(19). Although the transporter has been functionally demonstrated, it has not yet been cloned or characterized.…”