G. Halet et al., Effects of hindlimb suspension on cytosolic Ca2+ and [H-3]ryanodine binding in cardiac myocytes, AM J P-HEAR, 45(4), 1999, pp. H1131-H1136
Citations number
24
Categorie Soggetti
Cardiovascular & Hematology Research
Journal title
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
Effects of a 14-day hindlimb suspension were examined on [H-3]ryanodine bin
ding to rat ventricular microsomes and on cytosolic Ca2+ concentration ([Ca
2+](i)) and voltage-dependent Ca2+ channels in isolated ventricular myocyte
s. In suspended rats, the amplitude of the twitch [Ca2+](i) transient was i
ncreased without significant modifications of the basal [Ca2+](i) and sarco
plasmic reticulum content. Because cell capacitance, L-type Ca2+-current de
nsity, and Ca2+-channel gating were not significantly modified after suspen
sion, the increase in [Ca2+](i) was expected to reside in a change in ryano
dine receptors. Scatchard analysis of [H-3]ryanodine binding revealed that
suspension enhanced binding by increasing the affinity of the receptors for
[H-3]ryanodine without affecting the maximal binding capacity. Both Ca2+-r
elease channel activity and [H-3]ryanodine binding are modulated by Ca2+. H
owever, the Ca2+ sensitivity of [H-3]ryanodine binding remained unchanged a
fter suspension. Taken together, these results suggest that the increase in
twitch [Ca2+](i) transients after suspension may result from a change in t
he intrinsic properties of the ryanodine receptors but not from a change in
the expression level of these receptors.