Endothelium-dependent gender differences in responsiveness of rat aortic smooth muscle to reduction in extracellular magnesium and sodium ions.
Possible gender differences in contractile responses to reduction in extracellular Mg2+ ([Mg2+]0) and [Na+]0 in isolated aortic rings and strips from adult rats were investigated. In consonance with our previous studies, [Mg2+]0 withdrawal (0 mM Mg2+) and reduction in [Na2+]0 (total = 84 mM Na+) by replacement of NaCl with isosmolar amounts of sucrose in normal Krebs-Ringer bicarbonate (NKRB) induced significant increases of basal tone of aortic rings and strips in male, but not in female, rats. However, such tension development was observed in endothelium-denuded aortic preparations isolated from both sexes. No effects of indomethacin (10(-5) M) were found in any of the tissues tested. Adding 1.2 mM MgSO4 to the Mg2+ and Na(+)-deficient incubation media relaxed the tension increase to a normal basal level. The endothelium-dependent vasodilator responses to acetylcholine (10(-10) - 10(-6) M) of aortic rings from male or female rats in NKRB were not different. These results suggest that: (1) as in vascular smooth muscle cells, Mg2+ plays an important role in Ca2+ homeostasis in endothelial cells, probably via Na(+)-Ca2+ exchange and (2) sex steroid hormones may influence contractile responses of vascular smooth muscle by modifying endothelium function through such Mg(2+)-regulated internal Na(2+)-dependent Ca2+ entry.
Zhang
A M
AM
Department of Physiology, State University of New York Health Science Center at Brooklyn, Brooklyn.
Altura
B T
BT
Altura
B M
BM
D000109:Acetylcholine; D000818:Animals; D001013:Aorta, Thoracic / Q000502:physiology; D004730:Endothelium, Vascular / Q000502:physiology*; D005260:Female; D066298:In Vitro Techniques; D007474:Ion Exchange; D008274:Magnesium / Q000502:physiology*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012737:Sex Factors; D012964:Sodium / Q000502:physiology*; D014661:Vasoconstriction / Q000502:physiology
D012964:Sodium; D008274:Magnesium; D000109:Acetylcholine