Table 1

Endogenous effectors

Ca2+ releaseSingle channel[3H]Ryanodine binding
γPoAffinity (1/KD )Bmax
Ca2+ +1-a 0+1-a +1-a +1-a
Mg2+ 0
H+ 1-b 01-c 1-b 1-b 1-b
Fe2+ ndnd
Inorganic phosphate+1-d 0+1-d +1-d 0
Adenine nucleotides+0+++
Adenosine+1-e 0+1-e ndnd
cADPR+1-f 0+1-f +1-f +1-f
Palmitoyl carnitine+1-d 0+1-d (+)1-d (+)1-d
Sphingosine1-g ndnd
Spermine0+1-h 0
 Protein kinase A1-j +0++
 Endogenous CaMK II0(−)0
Calmodulin+/−1-k 0+/−1-k +/−1-k   
  • Summary of the effects of endogenous effectors in Ca2+ release, single-channel and [3H]ryanodine binding experiments. Only the most representative effectors are included in the table. In particular, substances whose action are controversial or incompletely characterized are omitted. Proteins interacting with the RyR also are omitted, except for calmodulin. See text for further details. Effects onKD and Bmax could not be distinguished in some cases.

  • 1-a The dose-response curve is bell-shaped, and the activation decreases at high concentrations.

  • 1-b At physiological pH, an acidification was inhibitory, but the dose-response curve is bell-shaped, and high pH may decrease Ca2+ release.

  • 1-c Channel conductance was reduced by acidification of thetrans chamber.

  • 1-d The effect is probably selective for the skeletal muscle channel.

  • 1-e The effect is probably selective for the cardiac channel.

  • 1-f The effect of cyclic ADPR is controversial and probably it is not physiologically relevant in striated muscle (see text for a full discussion).

  • 1-g Stimulation of Ca2+ release was observed at high (unphysiological) concentrations.

  • 1-h Effect observed only at very high (unphysiological) concentrations.

  • 1-i Only cardiac muscle effects are shown, because skeletal muscle effects are controversial.

  • 1-j Protein kinase G and PKC had similar effects in release and binding experiments.

  • 1-k Stimulatory effects were observed at submicromolar (< 0.1 μm) Ca2+, and inhibitory effects were observed at micromolar or millimolar Ca2+.

  • γ, channel conductance; +, increased; (+), increase has not been consistently reported; −, decreased; (−), decrease has not been consistently reported; 0, unchanged; nd, not determined.