Prostaglandin biosynthesis by fat body from the tobacco hornworm, Manduca sexta

We describe prostaglandin (PG) biosynthesis by microsomal-enriched preparations of fat body from larvae of the tobacco hornworm Manduca sexta. Four major PGs were synthesized under most experimental conditions, PGA 2, PGE 2, PGD 2 and PGF 2α. PGA 2, was the predominant product under most conditions. Unlike mammals, in which PGA 2, is generally thought to arise from non-enzymatic rearrangemets of PGE 2, the fat body preparations did not convert exogenous PGE 2 into PGA 2. These findings suggest that PGA 2 is an important fat body product that is synthesized by a route that does not involve PGE 2. The PG synthase activity and the overall profile of PG synthesis were sensitive to experimental conditions, including incubation time, temperature, and protein concentration. Optimal PG biosynthesis was observed with 1 mg of microsomal-rich protein, incubated at 30°C for 1–2 min. The fat body preparation is sensitive to two non-steroidal anti-inflammatory drugs, indomethacin and naproxen, both of which inhibited PG synthesis at low dosages.