Reference: Biol. Bull. 173: 92-109. (August, 1987) PHYSIOLOGICAL ROLES OF PROSTAGLANDINS AND OTHER EICOSANOIDS IN INVERTEBRATES DAVID W. STANLEY-SAMUELSON Dcj'ii.'-nnent of Entomological Sciences, University of California, Berkeley, California 94720 ABSTRACT Prostaglandins and other biologically active derivatives of polyunsaturated fatty acids have been detected in a large number of invertebrate species. A brief summary of the mammalian background of arachidonic acid metabolism is provided, and the physiological significance of these compounds in invertebrates is reviewed. Topics include regulation of ion flux, temperature regulation, reproductive biology, cell ag-gregation, and host-parasite interactions. Finally, perspectives on current and possi-ble future research are offered. INTRODUCTION The term eicosanoid was introduced and used by Corey et al. (1980) to describe the various biologically active derivatives of eicosapolyenoic fatty acids, especially arachidonic acid. So far, we know of four major groups of eicosanoids: the prostaglan-dins (PCs), the hydroperoxy-and hydroxyeicosatetraenoic acids (HPETEs and HETEs), the leukotrienes (LTs), and the lipoxins (LXs). Interest in the significance of eicosanoids in the biology of mammals stems from physiological studies conducted in the early twentieth century. In the earliest reference to one group of eicosanoids, the PGs, Jappelli and Scafa (1906) noted that extracts of dog prostrate glands caused paralysis of central respiratory control and changed heart rates when injected into dogs and rabbits. The discovery of PG pharmacological activity in human seminal fluids (Kurzrok and Lieb, 1930) probably marks the beginning of the detailed studies of the clinical significance of these compounds. Elucidation of the chemical structures of PGs in the early 1960's (Bergstrom et al., 1962a, b) greatly increased the pace of research and discovery, hindered in that decade mainly by the limited availability of working quantities of purified compounds. It is now known that PGs are present and play important roles in almost all mammalian tissues and fluids (Horrobin, 1978). Examples of PG action include pathophysiological actions such as mediation of the inflammatory response (which we commonly block by ingestion of aspirin) and par-ticipation in the blood-clotting cascade, as well as physiological actions such as con-traction of smooth muscle. The growth of PG research began with initial physiological observations, along with isolation and structural determinations of individual PGs. This was followed by the development of techniques to produce PGs in a commercially profitable way for clinical and biological studies. Commercial production of PGs evolved from biosyn-thesis from appropriate precursor fatty acids using large-scale enzyme preparations, through the discovery of naturally occurring sources of PGs and of intermediates in chemical synthesis to economical total synthesis. Hence, the first report of PGs in Received 15 April 1987; accepted 26 May 1987. Abbreviations: PG == prostaglandin, LT = leukotriene, HETE = hydroxyeicosatetraenoic acid, HPETE = hydroperoxyeicosatetraenoic acid, LX = lipoxin. 92
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