Metabolism of Isotopic Lactate by the Isolated Perfused Dog Gastrocnemius

Publisher Website
Google Scholar
Abstract
The metabolism of C13-lactate was studied in the isolated perfused dog gastrocnemius. Under the conditions employed, 12–13% of the respiratory CO2 was derived from the administered lactate (carboxyl-labeled) in unstimulated muscles, whereas 25–29% was so derived in muscle contracting at a rate of 2/sec. (from either carboxyl or α,ß-labeled lactate). Thus, the increase in the rate of conversion of lactate to CO2 associated with contraction was greater than the increase in the rate of CO2 production. Evidence for the conversion of administered lactate to glycogen was found only from the α,ß-labeled compound in unstimulated preparations given insulin and in the presence of moderate blood glucose levels. Such conversion was not demonstrated in any of the repetitively contracting muscles given carboxyl- or α,ß-labeled lactate or in unstimulated preparations administered carboxyl-labeled lactate.