Serum lactate dehydrogenase of normal, stressed, and yellow fever virus-infected rhesus monkeys

Serum lactate dehydrogenase enzyme (sLDH) was studied in both healthy and yellow fever virus (YFV)-infected young adult rhesus monkeys (Macaca mulatta). In healthy monkeys, significant variation (p less than 0.001) was observed for both total activity and isoenzyme distribution among the following comparisons: individual monkeys, different days, different times of day, and caged versus chair-restrained monkeys (until 7 da after chair restraint). However, variability of baseline values was reduced by the use of samples obtained from resting subjects at 9:00 am on at least 3 consecutive days. Normal total activity and isoenzyme distribution values were based on 148 determinations obtained from 73 healthy, caged monkeys. Both total activity and the proportion of the 5th isoenzyme fraction increased significantly (p less than 0.001) in the YFV-infected monkeys, beginning 90 hr postinfection, consistent with hepatocellular necrosis and release of isoenzymes into the serum. The assay for sLDH appears to be of value as a diagnostic indicator during the course of YFV infection in the rhesus monkey.