The actions of extracellular magnesium on isolated human detrusor muscle function.
The effects of increasing the extracellular magnesium concentration ([Mg]) on the in vitro mechanical and electrophysiological properties of isolated human detrusor smooth muscle have been investigated. Raising extracellular Mg reduced the magnitude of the electrically-induced phasic contractions as well as spontaneous contractions. A similar increase in the [Mg] reduced the magnitude of the inward Ca2+ current associated with the action potential as well as shifting the activation curve to more positive potentials. Spontaneous oscillations of intracellular Ca2+ could be observed in some isolated cells and such activity was also abolished by raising the extracellular [Mg]. It is proposed that the contractile effects of raised extracellular Mg are mediated by an action on the inward Ca2+ current and that these observations suggest a means whereby normal and abnormal detrusor contractions might be effectively regulated.
Montgomery
B S
BS
Department of Physiology, United Medical School of Guy's Hospital, London.
Thomas
P J
PJ
Fry
C H
CH
D002118:Calcium / Q000493:pharmacokinetics; D006801:Humans; D008274:Magnesium / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000502:physiology*; D001743:Urinary Bladder / Q000502:physiology
D008274:Magnesium; D002118:Calcium