Jde. Hart et Af. Dulhunty, Nitric oxide activates or inhibits skeletal muscle ryanodine receptors depending on its concentration, membrane potential and ligand binding, J MEMBR BIO, 173(3), 2000, pp. 227-236
We show that rabbit skeletal RyR channels in lipid bilayers can be activate
d or inhibited by NO, in a manner that depends on donor concentration, memb
rane potential and the presence of channel agonists. 10 mu M S-nitroso-N-ac
etyl-penicillamine (SNAP) increased RyR activity at -40 mV within 15 sec of
addition to the cis chamber, with a 2-fold increase in frequency of channe
l opening (F-o). 10 mu M SNAP did not alter activity at +40 mV and did not
further activate RyRs previously activated by 2 mM cis ATP at +40 or -40 mV
. In contrast to the increase in F-o with 10 mu M SNAP, 1 mM SNAP caused a
2-fold reduction in F-o but a 1.5-fold increase in mean open time (T-o) at
-40 mV in the absence of ATP. 1 mM SNAP or 0.5 mM sodium nitroprusside (SNP
) induced similar to 3-fold reductions in F-o and T-o at +40 or -40 mV when
channels were activated by 2 mM cis ATP or in channels activated by 6.5 mu
M peptide A at -40 mV (peptide A corresponds to part of the II-III loop of
the skeletal dihydropyridine receptor). Both SNAP-induced activation and S
NAP/SNP-induced inhibition were reversed by 2 mM dithiothreitol. The result
s suggest that S-Nitrosylation or oxidation of at least three classes of pr
otein thiols by NO each produced characteristic changes in RyR activity. We
propose that, in vivo, initial release of NO activates RyRs, but stronger
release increases [NO] and inhibits RyR activity and contraction.