Effect of epinephrine on net lactate uptake by contracting skeletal muscle

The purpose of this study was to determine the effect of epinephrine on net lactate (La-) uptake at constant elevated blood La- concentration and stea dy level metabolic rate (O-2 uptake) in the canine gastrocnemius-plantaris muscle in situ. Infusion of La-/lactic acid (pH 3.5) established a mean art erial blood La- concentration of similar to 10 mM while normal blood-gas an d pH status were maintained as the gastrocnemius-plantaris was stimulated w ith tetanic trains at a rate of one contraction every 4 s. After steady-sta te control measures, epinephrine was infused for 35 min at rates that produ ced a high physiological concentration with (Pro; n = 6) and without (Epi; n = 6) beta -adrenergic-receptor blockade via propranolol. Net La- uptake v alues during the control conditions were not significantly different betwee n trials (Epi: 0.756 +/- 0.043; Pro: 0.703 +/- 0.061 mmol.kg(-1).min(-1)). Steady level O-2 uptake averaged similar to 69.5 ml.kg(-1).min(-1) for both control conditions and did not significantly change over the course of the experiments in either set of trials. Epi experiments resulted in a signifi cantly reduced net La- uptake (0.346 +/- 0.088 mmol.kg (1).min(-1) after 5 min of infusion) compared with control value at all sample times measured. However, net La- uptake was not significantly different from control at any time during Pro (0.609 +/- 0.052 mmol.kg(-1).min(-1) after 5 min of infusi on). When the change from the respective control values for net La- uptake was compared across time for both series of experiments, Epi resulted in a significantly greater change from control than did Pro. This study suggests that epinephrine can have a profound effect on net La- uptake by contracti ng muscle and that these effects are elicited through beta -adrenergic-rece ptor stimulation.