Detection and bioassay of pharmacologically active substances released by arachidonic acid from guinea-pig perfused lungs

Abstract

A differential bioassay system was used to detect and estimate the active substances released by AA from guinea-pig perfused lungs. The lung perfusate superfused 5 assay tissues in series, a rabbit aorta (RA 1), a rabbit coeliac (RCA) or mesenteric artery (RMA), another rabbit aorta (RA 2), a rat stomach strip (RSS), and a rat colon (RC). A coil was incorporated into the cascade between tissue 2 and 3 such that the lung perfusate was delayed for 2 min at 37°C at this point. This effectively removed the labile TxA 2 from the perfusate after quantitation on the vascular tissues, allowing more accurate assay of the more stable PGs present. Any endoperoxides in the perfusate were detected by the contractions of the RA 2 under the delay coil. PGE 2, PGF 2α and PGI 2 were measured on the RSS and the presence of PGI 2 detected by inhibition of spontaneous contractions of the RC. The bioassay tissues were calibrated with standard solutions of AA metabolites where possible. AA (2.5–10 μg) released predominantly TxA 2 and PGI 2 from guinea-pig lungs, while very little endoperoxide, PGE 2, and PGF 2α,were detected.