Eicosanoid synthesis by purified thrombocytes and erythrocytes from warm- and cold-acclimated American bullfrogs (Rana catesbeiana).
Amphibian blood plays an important role in eicosanoid synthesis. Although clotting frog blood produces eicosanoids, the cellular source of prostaglandins and thromboxanes in bullfrog blood is unknown. Thromboxane (TX)B2 synthesis from purified thrombocytes was affected by 30-day cold-acclimation at 5 degrees, but not PGE2 or leukotriene (LT) synthesis. Although no cyclooxygenase activity has been found in human erythrocytes, frog erythrocytes were capable of forming cyclooxygenase products, but the amounts were lower than those produced by thrombocytes. Additionally, there was no effect of cold exposure on eicosanoid production by isolated erythrocytes. Similar to some mammalian nucleated white blood cells, nucleated bullfrog thrombocytes and erythrocytes produced leukotrienes. The production of eicosanoids by thrombocytes was stimulated by A23187 and thrombin. Erythrocytes were stimulated by A23187. Control synthesis by erythrocytes and thrombocytes was inhibited by 5 microM indomethacin (cyclooxygenase pathway) or nordihydroguaiaretic acid (5-lipoxygenase pathway) and cyclooxygenase products were increased in the presence of nordihydroguaiaretic acid. Thrombin stimulation of eicosanoid production by thrombocytes was inhibited when the inhibitors were present prior to the final centrifugation of the cell isolation. The results suggest that cold exposure can affect eicosanoid synthesis in thrombocytes, but not erythrocytes, and that thrombocytes are a major source of eicosanoids in bullfrogs. The production of cyclooxygenase and lipoxygenase products by nucleated erythrocytes and thrombocytes suggests a role for these compounds in hemostasis and inflammatory responses in these animals.
Wang
X
X
Department of Biology, New Mexico State University, Las Cruces 88003, USA.
Herman
C A
CA
D000064:Acclimatization; D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D000001:Calcimycin / Q000494:pharmacology; D002469:Cell Separation; D003080:Cold Temperature; D015777:Eicosanoids / Q000096:biosynthesis*; D004906:Erythrocyte Count; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D006358:Hot Temperature; D006801:Humans; D007476:Ionophores / Q000494:pharmacology; D008297:Male; D010976:Platelet Count; D011892:Rana catesbeiana / Q000097:blood*; D013045:Species Specificity; D013917:Thrombin / Q000494:pharmacology
D015777:Eicosanoids; D007476:Ionophores; D000001:Calcimycin; D013917:Thrombin