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 [Amblyamma 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 μl of saliva contained higher ts-PLA₂ activity than saliva secreted thereafter. Phospholipase A₂ was identified in the saliva of artificially fed ticks indicating that ts-PLA₂ is a physiological component of tick saliva.