title: Contractility of alpha-toxin permeabilized ventricular muscle of guinea pig.
abstract: This study explored whether Staphylococcus aureus alpha-toxin can permeabilize the ventricular muscle and whether the treatment can leave cardiac membrane receptors, intracellular Ca2+ stores and the Ca2+ sensitivity of myofilament without damage. After alpha-toxin treatment, the trabeculae from guinea-pig ventricles developed tension at very low Ca2+ concentration ([Ca2+]) (approximately 0.6 microM) in high K+ solution. The trabeculae could contract transiently with 20 mM caffeine after incubating the muscle in a solution containing 0.5 microM [Ca2+]. Phenylephrine (20 microM) with or without GTP gamma S, a non-hydrolyzable analogue of GTP, in the incubating solution did not change the caffeine-induced tension transient. After loading intracellular Ca2+ stores with Ca2+, Ca2+ could be released from the stores by the [Ca2+] of 1.6 microM since the caffeine-induced tension transient was smaller than without Ca2+ releasing protocol. Phenylephrine with or without 100 microM GTP in the releasing solution did not modify the caffeine-induced tension transient. When the muscle was bathed in 1.6 microM Ca2+ solution containing 5 mM EGTA, the developed tension was maintained stably for more than 2 h. Phenylephrine with or without GTP, GTP alone, or 20 microM inositol 1,4,5-trisphosphate (InsP3) did not change the maintained tension. The amplitude and the rate of spontaneous contractions, induced at the free [Ca2+] around 0.5 microM, were not modified by phenylephrine, with or without GTP, and InsP3. These results show that alpha-toxin is useful at least to permeabilize the cardiac muscle to ions and small molecules without damaging the internal membrane and contractile machinery.
authors.affiliation: Department of Physiology, School of Medicine, Fukuoka University, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Ohba
authors.forename: H
authors.initials: H
authors.lastname: Kawata
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D003285:Contractile Proteins / Q000378:metabolism; D005260:Female; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000378:metabolism*; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D008297:Male; D009200:Myocardial Contraction; D009206:Myocardium / Q000378:metabolism*; D009991:Oscillometry; D010656:Phenylephrine / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D010738:Type C Phospholipases / Q000378:metabolism*
chemical_list: D003285:Contractile Proteins; D010656:Phenylephrine; D015544:Inositol 1,4,5-Trisphosphate; D006160:Guanosine Triphosphate; D010738:Type C Phospholipases; D002118:Calcium