Comparison of foetal metabolic differentiation in three cattle muscles

Metabolic differentiation of Semitendinosus (ST), Cutaneus trunci (CT) and Masseter (MA) in cattle foetuses aged from 110 to 260 days was studied by m easuring isocitrate dehydrogenase (ICDH, oxidative) and lactate dehydrogena se (LDH, glycolytic) activities. The five LDH isoenzymes were separated by electrophoresis and assayed by densitometry. ICDH activity increased from 2 10 days onwards in the three muscles but more intensively in MA (oxidative) . LDH activity increased from 170 days onwards in ST, 180 days onwards in C T and only from 210 days onwards in MA and was higher in the glycolytic mus cles (ST and CT). The proportion of the LDH-M subunit increased during foet al life in glycolytic muscles. At 110 days, it was higher in CT, intermedia te in ST and lower in MA. These results show that 1) metabolic differentiat ion of bovine muscle begins during the last third of foetal life and 2) the proportion of the LDH-M subunit seems to be related to the contractile typ e of adult muscle from the first stages of foetal life. (C) Inra/Elsevier, Paris.