Activity of Some Enzymes in Developing Muscle of the Pig

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Extract: Total phosphorylase, lactic dehydrogenase (LDH), and glutamate-oxaloacetate transaminase (GOT) activities and lactic dehydrogenase isozyme patterns were determined on logissimus (white) and trapezius (red) muscles of developing pigs between the ages of 1 day and approximately 24 weeks. All enzyme activities were similar in both muscles at day 1. Phosphorylase and LDH activities in longissimus muscle increased rapidly and by 24 weeks there was a 4- and 10-fold increase in activities for the two enzymes, respectively. The GOT activity also increased but not to the same extent. Phosphorylase, LDH, and GOT acitivities of the trapezius muscle increased about 2-fold as the animal matured. Phosphorylase and GOT activities peaked in both muscles and then declined to adult values whereas LDH increased to the adult level. The LDH isoymes 1 and 11 were the major isozymes and V was a minor isozyme in both muscles at day 1 of age. In the adult, V was the major isozyme in longissimus muscle and I and V were the major isozymes in trapezius muscle. Speculation: The muscle of developing pig undergoes biochemical changes associated with fiber type differentiation. The muscle, however, displays a unique grouping of fiber types, and we believe that this unusual morphology, occuring as it does in a normal biochemical environment offers a favourable experimental model for study of the basis of differentiation.