Direct effect of halothane and isoflurane on the function of the sarcoplasmic reticulum in intact rabbit atria.
The negative inotropic effect of halothane and isoflurane on potentiated-state contractions of isolated rabbit atria in a normal Ca2+ (2.5 mM) medium was compared with the force depression in low Ca2+ media without an anesthetic. When this comparison was made in the presence of 1 microM ryanodine so that the force of contraction was dependent only upon transsarcolemmal Ca2+ influx with no Ca2+ contribution from the sarcoplasmic reticulum (SR), the force of contraction was depressed equally by 0.6% halothane in a normal Ca2+ medium and by a 1.5 mM Ca2+ medium without the anesthetic. Similarly, 1.0% halothane or 1.5% isoflurane and a 1.0 mM Ca2+ medium were equally depressant as were 2.4% isoflurane and a 0.5 mM Ca2+ medium. In the absence of ryanodine, where the atrial contractile activity is largely dependent on Ca2+ released from the SR, 0.6% halothane in the normal Ca2+ medium depressed contractile force by 32%, whereas the force was depressed by only 16% in the 1.5 mM Ca2+ medium without the anesthetic. Similar results were obtained when the effects of 1.0% halothane and of 1.0 mM Ca2+ were compared. In contrast, the force of contraction measured in the absence of ryanodine was not at all inhibited by 1.5% isoflurane and minimally (11%) inhibited by 2.4% isoflurane. Consequently, the force depression by isoflurane was less than that found in the low Ca2+ media.(ABSTRACT TRUNCATED AT 250 WORDS)
Komai
H
H
Department of Anesthesiology, University of Wisconsin, Madison 53792.
Rusy
B F
BF
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D003470:Culture Media; D006221:Halothane / Q000494:pharmacology*; D006321:Heart / Q000502:physiology*; D006325:Heart Atria; D066298:In Vitro Techniques; D007530:Isoflurane / Q000494:pharmacology*; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000648:ultrastructure; D009994:Osmolar Concentration; D011817:Rabbits; D012433:Ryanodine / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000502:physiology*
D003470:Culture Media; D012433:Ryanodine; D007530:Isoflurane; D002118:Calcium; D006221:Halothane