Relaxation and polarization of precontracted rat aortic smooth muscle by sodium nitrite and an L-type channel blocker.
Membrane potential (MP) is essential for smooth muscle (SM) contraction, mainly by determining the activity of L-type Ca2+ channels (Ca(L)). Although a widely used SM model, there are few electrophysiology studies in rat aorta.


OBJECTIVE
We investigated the mechanism of SM relaxation induced by NaNO2 in comparison with a Ca(L) blocker.


METHODS
The dynamic MP-force relation was studied in de-endothelised rat aorta rings during contraction by 40 mM K+ or 0.01 mM phenylephrine (PHE) and relaxation by 0.01 mM methoxy-verapamil (D600) or 0.1 mM NaNO2.


RESULTS
We confirm data on resting MP and depolarization by K+ or PHE. MP and Ca(L) are essential for K+ contraction and have little involvement in PHE contraction. NaNO2 polarization is not positively correlated with the relaxing effect.


CONCLUSIONS
Our studies on the MP-force relation provide novel information regarding the excitation-contraction coupling in SM. Polarization seems to be just an additional mechanism within nitrite-induced relaxation and may not involve K+ channel activation.
Serban
D N
DN
Department of Physiology, School of Medicine, "Gr.T. Popa" University of Medicine and Pharmacy Iaşi.
Serban
Ionela Lăcrămioara
IL
Oprişa
Cristina
C
Petrescu
Gh
G
D000818:Animals; D001011:Aorta / Q000187:drug effects*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D020746:Calcium Channels, L-Type / Q000187:drug effects*; D004359:Drug Therapy, Combination; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D012977:Sodium Nitrite / Q000494:pharmacology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D014662:Vasoconstrictor Agents; D012977:Sodium Nitrite