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The cyclo-oxygenase pathway in the avascular heart of the frog, Rana esculenta L.

  • Author(s): Ghiara, P
  • Parente, L
  • Piomelli, D
  • et al.
Abstract

1. 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. 2. Using both this technique and radioimmunoassay determination, the cyclo-oxygenase pathway in perfused frog heart has been investigated. 3. Arachidonate (AA) (2-20 μg) 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 × 10-5M). 4. Radioimmunoassay determination of PGE2, TXB2and 6-keto-PGF1αin frog heart effluent, before and after AA injection (20 μg), gave the following yields (ng/ml of effluent). Basal: PGE2= 0.45 ± 0.15; TXB2= 0.46 ± 0.13; 6-keto-PGF1α- 2.21 ± 0.3. Following AA: PGE2= 1.55 ±0.35; 6-keto-PGF1α= 3.4 ± 0.4; TXB2= 1.00 ± 0.06. 5. 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. © 1984.

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