The cyclo-oxygenase pathway in the avascular heart of the frog, Rana esculenta L.
A modification of Vane's cascade is reported, allowing the superfusion bioassay of prostaglandin-like substances (PLS) in the outflow of isolated and perfused heart of the frog Rana esculenta L. Using both this technique and radioimmunoassay determination, the cyclo-oxygenase pathway in perfused frog heart has been investigated. Arachidonate (AA) (2-20 micrograms) injected into the perfusing fluid, was transformed by the heart into PLS, as shown by the response of the bioassay tissues (rat stomach strip, chick rectum, rat colon). A compound capable of relaxing rabbit mesenteric artery and a rabbit aorta contracting substance were also generated. The release was inhibited by indomethacin (1.0 X 10(-5)M). Radioimmunoassay determination of PGE2, TXB2 and 6-keto-PGF1 alpha in frog heart effluent, before and after AA injection (20 micrograms), gave the following yields (ng/ml of effluent). Basal: PGE2 = 0.45 +/- 0.15; TXB2 = 0.46 +/- 0.13; 6-keto-PGF1 alpha = 2.21 +/- 0.3. Following AA: PGE2 = 1.55 +/- 0.35; 6-keto-PGF1 alpha = 3.4 +/- 0.4; TXB2 = 1.00 +/- 0.06. Our results suggest that prostacyclin is a major product of the cyclo-oxygenase pathway in frog perfused heart. The biological significance of this finding is discussed in relation to both the absence of a coronary circulation in amphibians and to the spongy nature of frog myocardium.
D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism; D001681:Biological Assay; D002645:Chickens; D003331:Coronary Vessels; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009206:Myocardium / Q000201:enzymology*; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*; D011453:Prostaglandins / Q000378:metabolism; D011817:Rabbits; D011863:Radioimmunoassay; D011893:Rana esculenta / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013928:Thromboxane A2 / Q000378:metabolism; D014319:Triturus / Q000378:metabolism
D001095:Arachidonic Acids; D011453:Prostaglandins; D016718:Arachidonic Acid; D013928:Thromboxane A2; D011451:Prostaglandin-Endoperoxide Synthases