Effects of isoflurane on [Ca2+]i, SR Ca2+ content, and twitch force in intact trabeculae.
The goal was to test whether isoflurane exerts its depressant effect on the heart by mainly affecting the intracellular Ca2+ transient [Ca2+]i. Intact rat ventricular trabeculae, paced at 0.5 Hz and 30 degreesC with extracellular [Ca2+] ([Ca2+]o) of 2 mM, were used. The [Ca2+]i was monitored using fura 2 injected into the myoplasm. The sarcoplasmic reticulum (SR) Ca2+ content was estimated using rapid cooling with or without caffeine to induce Ca2+ release and contracture. A plot of peak twitch force versus peak [Ca2+]i transient with increasing isoflurane concentration declines linearly so that a 56% reduction in the peak [Ca2+]i transient would abolish twitch force. This relationship is intermediate between those obtained with lowering [Ca2+]o, which depresses twitch force through a reduction of the [Ca2+]i transient, and adding 2,3-butanedione monoxime, which reduces the responsiveness of the contractile system to [Ca2+]i. The isoflurane effect is different from that of halothane with respect to both the above relationship and the rapid-cooling response. Isoflurane abolishes the ability of rapid cooling to liberate Ca2+ from the SR.
Jiang
Y
Y
Department of Anesthesia Research Laboratories, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
Julian
F J
FJ
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002138:Calibration; D004558:Electric Stimulation; D016257:Fura-2; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D007530:Isoflurane / Q000494:pharmacology*; D007700:Kinetics; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011914:Rats, Inbred BN; D011917:Rats, Inbred Lew; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000502:physiology*; D013050:Spectrometry, Fluorescence / Q000379:methods; D013696:Temperature; D013997:Time Factors
D002110:Caffeine; D007530:Isoflurane; D002118:Calcium; D016257:Fura-2