A perfused ruminant muscle preparation

Abstract

SummaryA technique was developed for the continuous retrograde perfusion of the muscle of the right crus. The hemidiaphragm was perfused for 3 h with a semi-synthetic medium, containing fresh sheep erythrocytes. The metabolic integrity of the perfused muscle was examined. Visual appearance was satisfactory. Perfusion pressure remained constant throughout the perfusion period. An adequate perfusate flow rate (approximately 8 ml/min) was maintained over the perfusion period. Perfusion pressure and flow rate were proportional. Perfusion was complete as indicated by staining with dye and by latex casts of perfused vessels, but there were indications of heterogeneity of perfusion (the dorsal and ventral ends of the organ). Histological changes following perfusion were minor, and the perfused muscle appeared normal under an electron microscope, with the exception of a loss of cytoplasmic granules. Increases in muscle water content (2·3%) and extracellular space were small. Muscle adenosine triphosphate (ATP) and adenosine diphosphate (ADP) concentrations declined significantly following perfusion but ATP/ADP ratio increased significantly. Muscle glycogen content was maintained only when exogenous insulin was added to the medium; significant losses occurred following perfusion in the absence of insulin. Only 2–3% of tissue glutamate-pyruvate transaminase and glutamate-oxaloacetate transaminase were released into the medium over the perfusion period, but approximately 20% of muscle potassium was lost. Lactate was produced by the perfused sheep hemidiaphragm at a rate higher than those that have been reported for the perfused rat hind-limb, but lower than those reported for perfused rat diaphragm. Ratio of lactate/pyruvate produced by the perfused muscle was also higher than values reported for the rat hind-limb. The perfused muscle actively incorporated labelled amino acids into protein, but estimated protein synthetic rate in the absence of exogenous insulin was only approximately 50% of rates reported for diaphragm musclein vivo. While the isolated, perfused sheep hemidiaphragm shows several deficiencies, it does provide a useful method for the study of ruminant muscle metabolism under carefully controlled conditionsin vitro, and overcomes many of the disadvantages of other techniques that are currently available.