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, Amblyomma americanum, to take up, incorporate and redistribute [H-3]arachidonic acid was examined. Uptake of arachidonic acid was concentration dependent-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 entering the glands was esterified and found only in the phospholipid (similar to 80%) and triglyceride (similar to 10%). Essentially no radioactivity was associated with the diglyceride fraction and none with phosphatidic acid indicating de novo phospholipid synthesis was negligible. Phospholipid synthesis via acylation of lysophospholipids (the Lands pathway) was indicated by the rapidity of the synthesis (< 2 min) and the 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 incorporated primarily into PC, but as the incubation proceeded PE contained an increasing proportion of the label. The proportion of [H-3]arachidonate incorporated into triglyceride increased at higher media concentrations of arachidonic acid. The roles of lysophosphatide acyltransferase, transacylase and diglycerol acyltransferase in the distribution of arachidonate in tick salivary glands are discussed.