UPTAKE, INCORPORATION AND REDISTRIBUTION OF ARACHIDONIC-ACID IN ISOLATED SALIVARY-GLANDS OF THE LONE STAR TICK

The ability of isolated salivary glands from the lone star tick, Ambly omma americanum, to take up, incorporate and redistribute [H-3]arachid onic acid was examined. Uptake of arachidonic acid was concentration d ependent-a single salivary gland incorporated up to similar to 2.8 mu g arachidonic acid in 60 min. Over 90% of the [H-3]arachidonate enteri ng the glands was esterified and found only in the phospholipid (simil ar to 80%) and triglyceride (similar to 10%). Essentially no radioacti vity was associated with the diglyceride fraction and none with phosph atidic acid indicating de novo phospholipid synthesis was negligible. Phospholipid synthesis via acylation of lysophospholipids (the Lands p athway) was indicated by the rapidity of the synthesis (< 2 min) and t he sensitivity to sulfhydryl-blocking agents. Within the phospholipids , [H-3]arachidonate was incorporated only into phosphatidylcholine (PC ) and phosphatidylethanolamine (PE). Initially [H-3]arachidonate was i ncorporated primarily into PC, but as the incubation proceeded PE cont ained an increasing proportion of the label. The proportion of [H-3]ar achidonate incorporated into triglyceride increased at higher media co ncentrations of arachidonic acid. The roles of lysophosphatide acyltra nsferase, transacylase and diglycerol acyltransferase in the distribut ion of arachidonate in tick salivary glands are discussed.