ACTIVE SKELETAL-MUSCLE METABOLISM AND TENSION PRODUCTION - THE INFLUENCE OF BIOPSIES

The influence of repeated sampling by the biopsy technique on skeletal muscle's metabolic and force-output responses was studied using the i n situ canine gastrocnemius preparation. The left muscle was stimulate d (8 V, 0.2 ms) for 1 h at 3 Hz. In the biopsy series (n = 9) muscle s amples were taken at rest, and at 0.5, 2, 5, 15, 30, 45, and 60 min of stimulation. In the control series (n = 8) the left and right muscles were quick-frozen in N2 immediately after the 60 min of stimulation. The two series were not different in blood flow, VO2, arterial or veno us [H+], muscle glycogen, or lactate release throughout the 60 min of activity. The lactate release was transient and was associated with an accumulation of intramuscular lactate and a period of rapid glycogeno lysis. The biopsy series had a modest but significantly (p < 0.05) hig her muscle lactate concentration both at rest and at the end of the co ntractions. The biopsy series also had less (p < 0.05) tension develop ment throughout the hour; however, the O2 cost per unit of tension dev elopment was not different between groups, nor was the rate of tension decline over time different. This together with the similarities in p erfusion, carbohydrate use, and lactate metabolism suggests that repea ted biopsies had minimal impact on the muscle. The technique allows th e collection of data over time; this improves the detail of experiment s and means that fewer animals are required for a study.