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 decapitation 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. Decapitation 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: [CP]/[Total Creatine] fell and [LA] rose significantly with exercise; resting [LA] was lower and increased with exercise; and metabolite variability was less with ether than with SP. We conclude that: anesthesia obscured the true effects of exercise on acid-base status by increasing [LA]a in the resting state; decapitation is unsuitable for the study of exercise effects on most muscle metabolites; 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.