Circadian variation of liver esterases

The circadian rhythm of liver esterase activity has been studied in rats maintained under highly standardized laboratory condition. They were housed in specially constructed climate rooms and subjected to an artificial 12 : 12 light-dark regimen. The total esterase was further differentiated to A esterase (E.C. 1.1.2) by using E 600 (Paraoxan), and a circadian rhythm for this enzyme also has been observed. During the lowest phase of total esterase activity, the higher phase for organophosphate-resistant esterase activity was observed.