Anesthetic effects on [H⁺]a and muscle metabolites at rest and following exercise

We determined the effects of ether, intra-arterial Na⁺ pentobarbital (SP) and decapitaion on arterial [H⁺] and labile metabolites in plantaris, diaphragm and intercostal muscles of rats at rest and following exhaustive treadmill exercise. 30-60 sec post-analgesia arterial [Lactate] ([LA]a) increased with both anesthetics. SP rats retained CO₂ resulting in mixed acidosis, while ether anesthetized rats hyperventilated and maintained pH. During recovery from exercise ether anesthesia had no effect but SP anesthesia caused CO₂ retention. Decenpitation of resting rats markedly decreased [CP] and elevated [LA] and [G6P] in all three muscles, thereby negating any subsequent exercise effects. The effects of ether differed from those of SP in that with ether anesthesia: (1) [CP]/[Total Creatine] dell and [LA] rose significantly with exercise; (2) resting [LA] was lower and increased with exercise; and (3) metabolite variability was less with ether than with SP. We conclude that: (a) anesthesia obscured the true effects of exercise on acid-base status by increasing [LA]a in the resting state; (b) decapitation is unsuitable for the study of exercise effects on most muscle metabolites; (c) ether anesthesia is most suitable for use in studies aimed at detecting exercise effects on muscle metabolites and for preserving arterial acid-base status closest to the unanesthetized state.