[Enzyme activities in serum of rabbits and rats-reference values and circadian alterations. Serum enzymes and factors that influence their activity,I (AUTHOR'S TRANSL)].

The activities of aspartate transminase (EC 2.6.1.1), alanine transminase (EC 2.6.1.2), alkaline phosphatase (EC 3.1.3.1), acid phosphatase (EC 3.1.3.2) leucine arylamidase (EC 3.4.1.1), aldolase (EC 4.1.2), lactate dehydrogenase (EC 1.1.1.27), malate dehydrogenase (EC 1.1.1.38) and cholinesterase (EC 3.1.1.7) were measured in serum of male rabbits and albino Wistar rats in dlplicate by means of microliter techniques. Furthermore, the diurnal alterations of enzyme activity were established in 8--10 animals of both species. Aspartate transaminase activity in the serum of rats was found to be significantly higher than in the serum of humans and rabbits, and essentially lower alkaline phosphatase values were obtained from the serum of rabbits in comparison with those found for the serum of humans and rats. Relatively high acid phosphatase and aldolase values as well as a very low cholinesterase activity were found in the serum of rabbits and rats. The mean malate dehydrogenase-activity was found to be twice as high as the mean lactate dehydrogenase, which is the contrary of the situation found in human serum. No significant diural alterations of the examined enzyme activities were established. The differences found between the animal and the human enzyme activities in serum are explained by species-determined peculiarities of metabolism or specific enzyme configuration.