Salivary gland homogenates of the sand fly Phlebotomus

insects and ticks. Perhaps for this reason a variety of salivary anti-hemostatic compounds are found in this diverse group of arthropods. Many different salivary anti-clotting and antiplatelet agents and vasodilators have been described. Salivary vasodilators range from inorganic nitric oxide to prostaglandins, various different peptides and enzymes that destroy norepinephrine. Several anti-clotting peptides, acting against different clotting factors, have been characterised, as have many anti-platelet substances acting on different pathways of platelet aggregation (Champagne, 1994; Ribeiro, 1995). Many salivary compounds that interfere with vertebrate hemostasis have additional effects on the host immune system, and these may in turn affect the fate of parasites transmitted during the act of blood feeding. For example, the New World sand fly Lutzomyia longipalpis has a very potent vasodilator, maxadilan (Lerner et al., 1991), in its saliva, and this also has immunosuppressive activities against macrophages and lymphocytes (Qureshi et al., 1996; Soares et al., 1998). This immunosuppression may be the reason that sand fly saliva potentiates the transmission of Leishmania parasites (Theodos et al., 1991; Titus and Ribeiro, 1988; Warburg et al., 1994). The Old World sand fly Phlebotomus papatasi does not have the vasodilator maxadilan, but its saliva nevertheless potentiates Leishmania transmission (Theodos et al., 1991). A protein phosphatase inhibitory activity has recently been found in this fly (Waitumbi and Warburg, 1998). P. papatasi salivary protein phosphatase inhibitor has been implicated in the downregulation of nitric oxide production by murine macrophages (Waitumbi and Warburg, 1998). In an attempt to find the salivary protein phosphatase inhibitor, we discovered large amounts (approximately 1 nmol per pair of glands) of 5′-AMP and adenosine in P. papatasi salivary glands, two substances with known vasodilatory (Collis, 1989) and anti-platelet (Edlund et al., 1987) functions. In the present study, salivary adenosine monophosphate is shown to be the previously observed salivary protein phosphatase inhibitor of P. papatasi.