The lactate dehydrogenase isoenzyme pattern in the overacting inferior oblique muscle

The lactate dehydrogenase (LDH) isoenzyme pattern in normal eye muscles of fetuses, children, and adults in overacting inferior oblique muscles of children was studied and compared. No significant differences were found between LDH isoenzyme activity in the horizontal and vertical recti. Isoenzyme fractions, by percentage, were distributed in these muscles in the order of III greater than IV greater than II greater than V greater than I. A significant difference, however, was noted between the LDH isoenzyme patterns of the inferior oblique muscle in normal adults and children. The percentages were in the orders of III greater than II greater than IV greater than V greater than I, and III greater than IV greater than II greater than V greater than I, respectively. The isoenzyme pattern in the overacting inferior oblique muscles of children was in the order of III greather than II greater than IV greater than V greater than I, identical to that of the adult control group. In addition, the overacting inferior oblique muscle of the children contained more H than M subunit than did the rectus muscle or the normal inferior oblique muscle of children by comparison.