~ Pergamon 0305-0491(95)00002-X Comp. Biochem, Physiol. Vol. 111B, No. 3, pp. 361-370, 1995 Copyright © 1995 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0305-0491/95 $9.50 + 0.00 Fatty acid composition of phospholipids and metabolism in rectal tissues of the African locust Bernard R. Fournier, Robert L. Wolff,* Michel Nogaro, Driss Radallah, Daniele Darret,t Jacky Larruet and Adrien Girardie Laboratoire de Neuroendocrinologie et U.R.A.C.N.R.S. 1138, Universit6 Bordeaux I, Avenue des Facult6s, 33405 Talence, France; *ISTAB, Laboratoire de Lipochimie, Universit6 Bordeaux I, Avenue des Facult6s, 33405 Talence, France; and tUR 8 INSERM, Cardiologie, CHR Haut-L6v6que, 33 Pessac, France Six groups of phospholipids were separated from the rectal tissues of the African locust: phospha- tidylcholine, phosphatidylethanolamine, phosphatidylinosituls, phosphatidylserine, sphingomyelin and cardiolipins. Saturated and unsaturated C18 components were abundant, as is generally observed in insects. Odd-chain (15: 0, 17: 0, 17:1) and long-chain fatty acids were also detected. Both 114C]18 : 2n-6 and [~4C]20:4n-6 were metabolized into prostaglandins (primarily PGEz) and HODEs, respectively, by the intervention of PGH-synthases. Incorporation of [t4C]18:2n-6 into phospholipids and neutral iipids or active exchanges of the fatty acid between both categories of iipids reflected different phospholipase, lipase and transferase activities. Triglycerldes appeared as a major source of fatty acids for locust rectum phospholipids. These data emphasize a major role of polyunsaturated fatty acids in insect renal physiology. Key words: Locust rectum; Phospholipids; Neutral lipids; incorporation; Metabolism; Exchanges; GLC; HPLC. Cornp. Biochern. Physiol. I l IB, 361-370, 1995. Fatty acids; Labelled PUFA Introduction The presence of different polyunsaturated fatty acids (PUFAs) has been demonstrated in phospholipids of insect tissues. Long-chain fatty acids, primarily arachidonic acid (20:4n-6), and their metabolites may intervene in physiological processes such as reproduction (Loher et al., Correspondence to: B. R, Fournier., Laboratoire de Neuro- endocrinologie et U.R.A., C.N,R.S. 1138, U.F.R. de Biologie, Universit~ Bordeaux I, Avenue des Facult6s, 33405 Talence, France. Tel. (33) 56 84 89 14; Fax (33) 56 84 87 50. Received 10 August 1994; accepted 6 December 1994. Abbreviations: DMSO, dimethylsulfoxide; GLC, gas liquid chromatography; HHT, 12-hydroxy-5,8,10-heptadeca- trienoic acid; HODEs, hydroxy-octodecadienoic acids; HPLC, high performance liquid chromatography; MG, DG and TG, mono-, di- and triglycerides, respectively; PC, phosphatidylcholine; PE, phosphatidylethanol- amine; P1, phosphatidylinositol; PS, phosphatidylserine; PUFAs, polyunsaturated fatty acids; SM, sphingo- myelins; TLC, thin layer chromatography. 1981; Della-Cioppa and Engelmann, 1984; Jurenka et al., 1988), glucido-energetic metab- olism (Van der Horst et aL, 1978; Stanley- Samuelson and Dadd, 1983, Bahjou et aL, 1990), or even hydric metabolism (Phillips et al., 1980; Petzel and Stanley-Samuelson, 1992). In insects, reabsorption of fluid (water and ions) has been assumed to be carried out by the rectum. Different signalization pathways may regulate this rectal function in response to anti- diuretic neuronal factors. The effects of neuro- parsin, a hormone from the storage lobes of the locust corpora cardiaca (Fournier and Girardie, 1988), are mediated via phosphoinositide turn- over and calcium (Fournier, 1990, 1991) owing to the intervention of phospholipase C and protein kinase C activities. Thus, it appears evident that phosphatidylinositols (PI) and phosphatidyl- serine (PS) are necessarily present in locust rectal cell membranes. 361