Oxygen Uptake of Atrioventricular Conducting Tissue of Beef Heart

Abstract

Slices of conducting tissue and ordinary heart muscle from fresh beef hearts were studied in a Warburg respirometer. Connective tissue detns. were made on all samples used: atrial muscle contained 7-14% wet wt. connective tissue; ventricular muscle, 4-20%; and conducing tissue, 20-42%. With a glucose substrate, conducting tissue had an avg. hourly uptake of .37 [plus or minus] .06 [mu] 1.O2/mg. wet wt of active tissue (corrected for connective tissue), while the Q02 of ventricular muscle was 1.76 [plus or minus] .04 [mu]l./mg./hr., and of atrial muscle, 1.55 [plus or minus] .08. [mu]l./mg./hr. A t test indicated that the O2 uptake by the conducting tissue was signigicantly lower than that of ordinary heart muscle (P < .01). A similar pattern was observed without added substrate, with added pyruvate, and also in the absence of Ca.