Effects of direct lytic factors from southern Chinese cobra venom on Ca2+ movement in rabbit aorta strip.
The purified direct lytic factors (DLF) from southern Chinese cobra (Naja naja atra) venom induced a contractile response in Ca(2+)-free Krebs' solution and a further increase in the tension following a subsequent addition of Ca2+ into bath. After depletion of intracellular Ca2+ pool by phenylephrine, DLF failed to induce any contractile response. In 45Ca2+ experiments, DLF increased both 45Ca2+ release and 45Ca2+ influx. Procaine 2 mmol.L-1 decreased the DLF induced 45Ca2+ release and 45Ca2+ influx by 67 +/- 23% and 46 +/- 32%, respectively. Nifedipine and verapamil 1 mmol.L-1 markedly inhibited the contractile response and the 45Ca2+ influx induced by DLF. These results suggest that DLF induces extracellular Ca2+ entry through voltage dependent Ca2+ channel and Ca2+ release from the intracellular Ca2+ pool which is sensitive to phenylephrine.
Chen
K M
KM
Department of Pharmacology, Sun Yat-Sen University of Medical Sciences, Guangzhou, China.
Guan
Y Y
YY
Sun
J J
JJ
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D004179:Cobra Cardiotoxin Proteins / Q000494:pharmacology*; D005260:Female; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009543:Nifedipine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011343:Procaine / Q000494:pharmacology; D011817:Rabbits; D014700:Verapamil / Q000494:pharmacology
D015220:Calcium Channels; D004179:Cobra Cardiotoxin Proteins; D010656:Phenylephrine; D011343:Procaine; D014700:Verapamil; D000252:Calcium-Transporting ATPases; D009543:Nifedipine; D002118:Calcium