The long-term objective of these studies is to define how (n-3) fatty acids mediate physiological processes regulated by prostaglandins and leukotrienes. Rats will be fed three levels of fish oil and pure 20:5(n-3) and 22:6(n-3) as sources of (n-3) fatty acids. The fatty acid composition of individual phospholipids from blood granulocytes, platelets, liver, heart, kidney and pancreas will be measured to define if various levels of (n-3) acids modify the membrane fatty acid composition of circulating cells differently from tissues which also make autocoids. Platelets and granulocytes from the different groups will be stimulated with agonists to titrate whether fatty acid compositional changes correlate with altered autocoid synthesis and lipolytic activity. Metabolites will be separated by high performance liquid chromatography and the relase and metabolism of specific acids will be quantitated by mass spectrometry using deuterated fatty acids as internal standards. These acids will be prepared by total synthesis. Enzymatic studies with intact human platelets and platelet homogenates, using selective inhibitors and activators, will define if platelets contain a second lipoxygenase which is rather specific for long chain (n-3) acids. Related studies will determine whether human granulocytes metabolize 20:5(n-3) into leukotrienes other than those containing their hydroxyl groups at carbons 5 and 12 and whether 22:6(n-3) is metabolized by the w8 lipoxygenase. The metabolites produced when 22:5(n-3) and 22:6(n-3) are incubated with platelets will be isolated and added to neutrophils to ascertain if they are further metabolized or alternatively modulate arachidonic acid metabolism from ionophore A23187 stimulated cells. Kidney and lung microsomes will be incubated with radioactive (n-3) acids to define if these acids are metabolized by these tissues. The rationale for these studies being that dietary (n-3) acids probably will result in an increase in their levels of tissues which also synthesize autocoids from arachidonic acid.
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