(1) In the mouse embryo there are changes in lactate dehydrogenase activity and isoenzyme pattern during the differentiation of cartilage and bone. (2) The specific activity of lactate dehydrogenase rises during chondrogenesis and falls during osteogenesis. (3) Identical isoenzyme transitions occur in parallel in both tissues: undifferentiated limb bud mesenchyme contains isoenzymes 1-5 whereas in both the cartilaginous and bony portions of a long bone developing from the mesenchyme, there is a progressive shift towards a predominance of the 'anaerobic' isoenzymes 4 and 5.
Aging Animals