Phospholipase A2 activity in salivary glands and saliva of the lone star tick (Acari: Ixodidae) during tick feeding.

Phospholipase A2 (PLA2) activity levels in tick [Amblyomma americanum (L.)] salivary glands and saliva were examined during tick feeding by using 14C-phosphatidylcholine as the substrate. Saliva produced by stimulating female ticks to salivate with dopamine contains PLA2 (ts-PLA2) activity. The ts-PLA2 activity level in saliva did not change significantly during tick feeding except for a decrease in the last rapid feeding phase (> 200 mg) and in replete ticks. Phospholipase A2 activity was higher in salivary glands of fed than unfed ticks, both in males and females; activity increased during tick feeding correlating with salivary secretory rates during tick feeding suggesting that much of the PLA2 activity measured in whole salivary glands is synthesized for subsequent secretion. During the time course of in vitro salivation, the first 10 microliters of saliva contained higher ts-PLA2 activity than saliva secreted thereafter. Phospolipase A2 was identified in the saliva of artificially fed ticks indicating that ts-PLA2 is a physiological component of tick saliva.