Distribution of lactate dehydrogenase isoenzymes in normal and inflamed bovine udders and milk.

The patterns of distribution of lactate dehydrogenase (LDH) isoenzymes were determined in normal and inflamed bovine udder tissues, in normal and mastitic milk-leucocytes and serum. LDH1 was the most common isoenzyme found in all the types of tissues examined, normal tissues contained the lowest proportions of LDH5 whereas the inflamed tissues and leucocytes from mastitic milk showed a higher proportion of LDH4 and LDH5. It seems that the origin of the elevated LDH in mastitic milk is the leucocytes and the parenchyma cells of the udder. The significance of the shift in the molecular forms of LDH isoenzymes is discussed in relation to possible alternations in energy metabolism in the inflamed bovine mammary gland.