METABOLISM OF ARACHIDONIC-ACID IN NEUTROPHILS FROM ALLOXAN-DIABETIC RABBITS

The production of 5-lipoxygenase products from arachidonic acid was investigated in polymorphonuclear leukocytes (PMNL) isolated from non-diabetic and alloxan-induced diabetic rabbits: (i) production of 5-hydroxyeicosatetraenoic acid, leukotriene B4, and the two 6-trans-leukotriene B4 isomers were significantly decreased in the PMNL of diabetic rabbits when compared to non-diabetic rabbits; (ii) production of LTB4 and 5-HETE from diabetic PMNL required the addition of Ca2+ and A23187 to a greater degree than control incubations; and (iii) the availability of substrate in the PMNL of diabetics was not a limiting factor for 5-lipoxygenase product formation. Alternative pathways of arachidonic acid metabolism were also evaluated: the recovery of exogenous leukotriene B4 and 5-hydroxyeicosatetraenoic acid were identical using PMNL from control and diabetic rabbits and peptido-leukotrienes were not detected by radioimmunoassay. The data suggests that the activity of 5-lipoxygenase and the production of 5-hydroperoxyeicosatetraenoic acid in the diabetic PMNL may be limiting factors since the formation of leukotriene B4, leukotriene B4 isomers, and 5-hydroxyeicosatetraenoic acid are depressed in PMNL of diabetic rabbits. Alternative pathways do not account for the conversion of arachidonic acid to other products nor are the elimination pathways for LTB4 and 5-HETE different. Decreased formation of 5-hydroxyeicosatetraenoic acid and leukotriene B4 could predispose diabetic subjects to infection due to a decrease in mediators leading to the local accumulation of PMNL in the inflammatory response.