ACTIVITY OF ADENOSINE DEAMINASE AND ITS ISOENZYMES IN SERUM OF PREGNANT BUFFALOES

Adenosine deaminase (ADA), an enzyme involved in purine catabolism, exists in two main isoenzymes forms, ADA1 and ADA2 which have different optimal pH, Michael’s constant and relative substrate specificity. Monocyte macrophages produce and release ADA2 when they are stimulated by infection (Gakis et al., 1995; Alrokayan, 2002) or when immunity is altered (Gakis, 1996). Pregnancy is associated with depressed cell mediated immunity (Gakis, 1996). Blood samples were obtained 6 hours post feeding from juggler vein of 66 pregnant and 13 non pregnant buffaloes. Serum was separated and used for the measurement of concentrations of ADA, ADA1 and ADA2. Activity of the ADA enzyme was measured spectrophotometrically using the method of Giusti and Galanti (1984), which is based on direct measurements of the ammonia produced when ADA acts in excess of adenosine. To distinguish ADA1 from ADA2, the activity was measured using the same techniques with erthyro9(2hydroxy3-nonyl) adenine. Erthyro-9(2hydroxy3nonyl) adenine is a potent inhibitor of only ADA1 isoenzyme (Gakis, 1996), showing the ADA2 activity. The activity of ADA1 was then calculated by subtracting the ADA2 activity from total ADA activity. Mean values (± SE) were computed for activities of ADA, ADA1 and ADA2 for pregnant and non pregnant buffaloes. Student’s T test was applied to ascertain the magnitude of difference in these activities between the two groups. Decreased (P<0.05) values of total serum ADA activity in the pregnant (all three trimesters) buffaloes compared to the non pregnant control group were recorded (Table 1). When the activities of isoenzymes were considered, ADA2 activity was lower (p<0.05) in pregnant than in non pregnant buffaloes. These results are supported by the findings of earlier workers, who suggested that ADA2 is involved in cellular immunity of human (Gakis, 1996). However, the ADA1 activity did not differ between the pregnant and non pregnant buffaloes. Similarly, the activities of total ADA, ADA1 and ADA2 did not differ among pregnant buffaloes of three trimesters. Similar results have reported in human by Martinez-Herndndez et al. (1990). It is concluded that reduced serum total ADA activity reflects decrease in ADA2 activity, which may be in part associated with depressed cell-mediated immunity during pregnancy. REFERENCES