Investigations into mechanisms of magnesium homeostasis in the isolated rat heart
type: CreativeWork
description: Magnesium (Mg24) is essential for normal functioning of the heart. It is the second most abundant divalent cation in living cells and plays vital roles in cellular regulation. Preservation of intracellular Mg 24 concentration ([Mg24]) is essential in the heart. The concentration of ionized Mg 24 is similar in both the extracellular and intracellular milieu of cardiac myocytes although a large electrochemical gradient exists which will tend to promote Mg24 influx across the sarcolemmal membrane. Therefore homeostatic mechanism(s) must exist which will extrude Mg 24 against this gradient. The existence of a Na/Mg2 counterport mechanism or an ATP driven pump for the extrusion of Mg 2 from the cell has been suggested. This work examines various possible mechanisms for Mg 24 extrusion. In a series of experiments, the effects on Mg 24 efflux and contractile force, of increased and decreased extracellular sodium [Na *], lithium chloride, specific ion channel inhibitors, osmotic shock, metabolic inhibition and global ischaemia, in the isolated, perfused (5 ml mm", 37°C) and paced (20V, I msec, 4-6 Hz) rat-heart were investigated in an attempt to characterize further, the mechanism of Mg 24 transport. Following a recovery period of 20 mm, the heart was perfused with a nominally Mg2tfree Krebs-Henseleit (1(H) solution, which facilitates the measurement of Mg24 in effluent samples using a spectroscopic method. Perfusion of the isolated heart with Mg 2 -free KH containing increased [Na], in chloride, nitrate, isethionate or sulphate forms, all promoted a large and significant (P C 0.05) Mg2t efflux. This efflux was, in general, accompanied by an increase in contractile force. Typically, net total Mg 24 efflux in elevated [Na']. (as NaCl), measured over a period of 10 min was 590.1 ± 26.7 ng (100 mg tissue)" (mean and SEM, n = 6) compared to 376.1 ± 17.9 ng (100 mg tissue)" (n = 7) in controls. However, lithium chloride also promoted significant (P C 0.05) increases in Mg 2 effl…
abstract: Magnesium (Mg24) is essential for normal functioning of the heart. It is the second most abundant divalent cation in living cells and plays vital roles in cellular regulation. Preservation of intracellular Mg 24 concentration ([Mg24]) is essential in the heart. The concentration of ionized Mg 24 is similar in both the extracellular and intracellular milieu of cardiac myocytes although a large electrochemical gradient exists which will tend to promote Mg24 influx across the sarcolemmal membrane. Therefore homeostatic mechanism(s) must exist which will extrude Mg 24 against this gradient. The existence of a Na/Mg2 counterport mechanism or an ATP driven pump for the extrusion of Mg 2 from the cell has been suggested. This work examines various possible mechanisms for Mg 24 extrusion. In a series of experiments, the effects on Mg 24 efflux and contractile force, of increased and decreased extracellular sodium [Na *], lithium chloride, specific ion channel inhibitors, osmotic shock, metabolic inhibition and global ischaemia, in the isolated, perfused (5 ml mm", 37°C) and paced (20V, I msec, 4-6 Hz) rat-heart were investigated in an attempt to characterize further, the mechanism of Mg 24 transport. Following a recovery period of 20 mm, the heart was perfused with a nominally Mg2tfree Krebs-Henseleit (1(H) solution, which facilitates the measurement of Mg24 in effluent samples using a spectroscopic method. Perfusion of the isolated heart with Mg 2 -free KH containing increased [Na], in chloride, nitrate, isethionate or sulphate forms, all promoted a large and significant (P C 0.05) Mg2t efflux. This efflux was, in general, accompanied by an increase in contractile force. Typically, net total Mg 24 efflux in elevated [Na']. (as NaCl), measured over a period of 10 min was 590.1 ± 26.7 ng (100 mg tissue)" (mean and SEM, n = 6) compared to 376.1 ± 17.9 ng (100 mg tissue)" (n = 7) in controls. However, lithium chloride also promoted significant (P C 0.05) increases in Mg 2 effl…
author: Hustler, Brenda Irene
language: en
keywords: C110 - Applied biology
date published: 1997-10
date modified: 2026-07-24T01:36:00Z
provider: University of Central Lancashire
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Central Lancashire