Expression of constitutive cyclo-oxygenase (COX-1) in rats with streptozotocin-induced diabetes; effects of treatment with evening primrose oil or an aldose reductase inhibitor on COX-1 mRNA levels.
Altered prostanoid metabolism participates in the pathogenesis of diabetic complications. The rate-limiting enzyme in the control of prostanoid metabolism is constitutive cyclo-oxygenase (COX-1). This study examined the possibility that altered prostanoid metabolism derives from altered COX-1 expression in those tissues from diabetic rats, with characteristic changes in prostanoid production and related haemodynamics. This account also describes a procedure for estimation of minute amounts of COX-1 mRNA by reverse transcription and competitive polymerase chain reaction (RT-cPCR) amplification. In streptozotocin-diabetic rats (STZ-D, 55 mg/kg body weight), compared with age-matched controls, the level of COX-1 mRNA (in attomoles/micrograms tRNA +/- 1SD) was significantly decreased in sciatic nerve (0.50 +/- 0.26 versus 0.89 +/- 0.32 in controls; P < 0.05) and thoracic aorta (3.99 +/- 1.67 versus 8.80 +/- 2.37 in controls; P < 0.05). There were no differences in COX-1 mRNA in diabetic and control rat kidney and retina, though there was a trend towards increased expression with diabetes in the latter. Evening primrose oil (EPO) treatment increased COX-1 mRNA in nerve and retina to levels in diabetic rats that were higher than those of non-diabetic controls (1.21 +/- 0.28 for nerve and 0.065 +/- 0.017 for retina, where control retinae gave 0.031 +/- 0.020-see above for nerve). Treatment of diabetic rats with an aldose reductase inhibitor was without effect on COX-1 mRNA levels in the tissues examined. This study demonstrates that the changes in COX-1 mRNA levels in diabetic rats are organ specific and suggests that altered prostanoid metabolism can, in part, be explained by altered COX-1 expression. Apart from providing arachidonate as substrate for COX, EPO stimulates COX-1 expression in some tissues.
Fang
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Department of Pharmacology, St. Bartholomew's, London, UK.
Jiang
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Tomlinson
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D000449:Aldehyde Reductase / Q000037:antagonists & inhibitors; D000818:Animals; D001013:Aorta, Thoracic / Q000201:enzymology; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D017931:DNA Primers; D003921:Diabetes Mellitus, Experimental / Q000201:enzymology*; D005228:Fatty Acids, Essential / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D007527:Isoenzymes / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D008041:Linoleic Acids; D008297:Male; D008565:Membrane Proteins; D031665:Oenothera biennis; D010938:Plant Oils; D016133:Polymerase Chain Reaction; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012584:Sciatic Nerve / Q000201:enzymology; D017965:gamma-Linolenic Acid
D001786:Blood Glucose; D017931:DNA Primers; D005228:Fatty Acids, Essential; D007527:Isoenzymes; D008041:Linoleic Acids; D008565:Membrane Proteins; D010938:Plant Oils; D012333:RNA, Messenger; C028498:evening primrose oil; D017965:gamma-Linolenic Acid; D000449:Aldehyde Reductase; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; C496513:Ptgs1 protein, rat