Trabeculae were carefully dissected from the appendages and, using 2-mm circular spring clips, were vertically suspended from a force transducer (Model 400; Cambridge Technology, Watertown, MA) in an organ bath maintained at 32°C.This lower temperature is used to prevent automaticity and facilitate pacing.The purpose of the current investigation was to determine any interaction between volatile anesthetics and preconditioning in a human model of simulated myocardial ischemia using anoxia (anoxic preconditioning).Human right atrial appendages were acquired from patients undergoing coronary artery bypass grafting surgery before bypass in accordance with guidelines of the University Human Investigation Committee.(-cyclohexyladenosine (CHA), 1% halothane, or 1.2% isoflurane in the presence and absence of 0.3 μm glibenclamide or 10 nm (APc DPCPX, isoflurane DPCPX) or 100 nm (CHA DPCPX) DPCPX for 5 min. Excluding a time control group (not shown), all muscles were made anoxic for 30 min (black area).Time points corresponding to data reported in figures 3 and 4are denoted by arrows. ( ) In the absence of oxygen, muscles underwent anoxic preconditioning (APc) alone or in the presence of 0.3 μm glibenclamide (Glib), 10 nm 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), 1% halothane, or 1.2% isoflurane.1B) to determine interaction of anesthetics with preconditioning anoxia.
Muscles that failed to generate 1 m N of force were not used in the experiments. ( ) In the absence of oxygen, muscles underwent anoxic preconditioning (APc) alone or in the presence of 0.3 μm glibenclamide (Glib), 10 nm 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), 1% halothane, or 1.2% isoflurane. Isolated trabeculae were equilibrated in a muscle bath for at least 1 h before application of one of the protocols.
, 5 mm HEPES, and 20 mm glucose adjusted to p H 7.3 with Na OH.
The tissue was then digested for 25–30 min with 1 mg/ml collagenase (Type I; Sigma, St.
Pretreatment force generated in muscles ranged from 1 to 17 m N and averaged 7.35 ± 8.8 m N (table 1).
Actual baseline values for developed force did not differ significantly among treatment groups.