Stability of lactate dehydrogenase, aspartate aminotransferase, alkaline phosphatase and tartrate resistant acid phosphatase in human saliva and gingival crevicular fluid in the presence of protease inhibitor

Abstract

The stability of aspartate aminotransferase (AST), lactate dehydrogenase (LDH), tartrate resistant acid phosphatase (TRAP) and alkaline phosphatase (ALP) activities from saliva and gingival crevicular fluid (GCF) with and without the addition of protease inhibitor (PI) at room temperature (RT; 25°C), 4°C and -20°C were investigated. AST, LDH, TRAP and ALP activities in saliva and GCF (n=9) with and without the addition of PI were assayed at 0 (control), 12, 24, 48, 72 h, one and two weeks. A paired t-test showed there were a significant differences (p<0.05) between LDH and TRAP activities in saliva, in the presence and without PI at all temperatures. ALP activity exhibited a significant difference in activity (p<0.05) in the presence and without PI at RT while no significant differences were observed at 4ºC and -20ºC. A significant difference (p<0.05) was observed in AST, LDH and TRAP activities (GCF) at RT and 4ºC in the presence and without PI. We conclude that PI is essential for maintaining stable enzyme activities in saliva and GCF.