Effect of propionyl-L-carnitine on L-type calcium channels in human heart sarcolemma.
Propionyl-L-carnitine (PC) protects perfused rat hearts against damage by ischemia-reperfusion. Activation of L-type calcium channel play a role on ischemia-reperfusion damage. Therefore, we studied the effect of PC on some properties of L-type calcium channels in an in vitro preparation from human myocardium sarcolemma (from patients with idiopathic dilated cardiomyopathy). Binding of the L-type calcium channel blockers isradipine [3H]-PN 200-110 (PN) to plasma membrane preparations revealed a single population of binding sites (total number: Bmax = 213 +/- 34 fM/mg protein and affinity: Kd = 152 +/- 19 nM; n = 6). The characteristics of these binding sites were evaluated in the presence and in the absence of Ca2+ and of calcium blockers (D-888, a verapamillike drug, and diltiazem). Incubation in a Ca2(+)-containing buffer increased the affinity of PN binding sites. Binding sites for PN were modulated by organic calcium channel blockers; in competition isotherms at 37 degrees C, D-888 (desmethoxyverapamil) decreased the PN binding, whereas diltiazem increased it. These results strongly suggest that the site labelled by PN is the voltage-operated calcium channel of the human myocardium. The addition of PC (1 mM) to plasma membranes labelled with PN at 37 degrees C decreased the affinity of the binding; this effect was counteracted by the addition of Ca2+ to the medium. This result was consistent with a competition between Ca2+ and PC. The effect of PC incubation at 4 degrees C was the opposite; at this temperature PC increased the affinity of the binding sites and the effect was obscured by Ca2+.(ABSTRACT TRUNCATED AT 250 WORDS)
Bevilacqua
M
M
Servizio di Endocrinologia, Ospedale L. Sacco (Vialba), Milano, Italy.
Vago
T
T
Norbiato
G
G
D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000378:metabolism / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects*; D002331:Carnitine / Q000031:analogs & derivatives* / Q000494:pharmacology; D002462:Cell Membrane; D046508:Culture Techniques; D006321:Heart / Q000187:drug effects*; D006801:Humans; D017275:Isradipine; D009206:Myocardium / Q000378:metabolism*; D010069:Oxadiazoles / Q000378:metabolism / Q000494:pharmacology; D011869:Radioligand Assay; D012508:Sarcolemma / Q000187:drug effects* / Q000378:metabolism; D014316:Tritium
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D010069:Oxadiazoles; D014316:Tritium; C003223:propionylcarnitine; D002331:Carnitine; D002118:Calcium; D017275:Isradipine