Salivary apyrase activity of some old world phlebotomine sand flies

Salivary gland homogenates of three Old World phlebotomine sand flies (Phlebotomus papatasi, P. argentipes and P. perniciosus) contained abundant ATPase and ADPase activities, indicating the presence of an apyrase activity. These activities had an optimum pH around 8.0 and were activated by Ca²⁺ but not Mg²⁺. Both hydrolytic activities and salivary protein content were significantly reduced after the female sand fly took a blood meal indicating a secretory fate for the enzymic activities and salivary gland contents during the feeding process. In contrast to the above mentioned species, the salivary apyrase activity of P. colabaensis is much less abundant. Salivary gland homogenates of P. papatasi, P. argentipes and P. perniciosus inhibited ADP-induced platelet aggregation of citrated rabbit platelet rich plasma. It is suggested that salivary apyrase activity, as in some other blood-sucking arthropods, helps the blood-feeding process by preventing host platelet aggregation.