ABSTRACT
The ability to control the cell volume under “resting” conditions and to regulate the cell volume when exposed to agonists or anisosmotic media are among the most fundamental properties of animal cells. Eicosanoids are oxygenated metabolites of 20-carbon polyunsaturated fatty acids, e.g., dihomo-γ-linolenic acid, arachidonic acid, and the well-known “fish oil” fatty acid, eicosapentaenoic acid. Arachidonic acid is liberated from the membrane after stimulation by hormones, autocoids, neurotransmitters, growth factors, antigens, or other stimuli. Released or exogenous arachidonic acid is either acylated into the cell membrane or converted to prostanoids via the cyclooxygenase pathway; leukotrienes and certain mono-, di-, and trihydroxy acids via the lipoxygenase pathways; or epoxyeicosatrienoic acids via the NADPH-dependent cytochrome P-450 “epoxygenase” pathway. Nonesterified arachidonic acid is transformed into prostaglandins by the heme-requiring, membrane-associated prostaglandin endoperoxidase synthase complex. Organic osmolytes are implicated in cell volume regulation of animal, plant, bacterial, fungal, and protist cells exposed to anisosmotic environments.
