title: Left ventricular hypertrophy in rabbits does not exaggerate the effects of halothane on the intracellular components of cardiac contraction.
abstract: Inhalational anesthetics and ventricular hypertrophy have adverse effects on cardiac muscle contraction. The effects of 1, 2, and 3% halothane on the contractile protein and sarcoplasmic reticulum, but not the sarcolemma, were examined in normal left ventricular tissue from rabbits that underwent a sham surgical procedure (n = 5) and in left ventricular hypertrophied tissue from surgically induced aortic coarctation (n = 7). Muscle samples were mechanically "skinned" to disrupt the sarcolemma. Fiber bundles were mounted in photodiode transducers and bathed in a series of solutions designed to examine the contractile protein [Ca2+]-tension responses or to examine Ca2+ storage by and release from the sarcoplasmic reticulum. Hill equation analysis of the [Ca2+]-tension relationship of the contractile protein was performed. Compared to normal muscle, hypertrophied muscle was associated with an 8.2% decrease in the [Ca2+] necessary for 50% maximum tension (more sensitive to Ca2+) (P less than 0.001) and an increase in the slope constant of 23% (P less than 0.001). In normal and hypertrophied tissue, each 1% of halothane incrementally decreased the contractile protein response to maximal [Ca2+] by 5% (P less than 0.01), increased the [Ca2+] at 50% maximum tension by 5% (P less than 0.01), and had no effect on the slope of the Hill equation. Halothane also inhibited Ca2+ storage by the sarcoplasmic reticulum. In normal muscle, 1, 2, and 3% halothane decreased the stored Ca2+ to 42, 22, and 9%, respectively, of Ca2+ storage without halothane (P less than 0.001). However, hypertrophied muscle demonstrated slightly less depression (P less than 0.05 by analysis of variance).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Anesthesiology, University of Washington School of Medicine, Seattle 98195.
authors.forename: G A
authors.initials: GA
authors.lastname: Rooke
authors.forename: J Y
authors.initials: JY
authors.lastname: Su
mesh_terms: D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D006332:Cardiomegaly / Q000378:metabolism*; D006221:Halothane / Q000494:pharmacology*; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009929:Organ Size / Q000187:drug effects; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism
chemical_list: D002110:Caffeine; D002118:Calcium; D006221:Halothane