CONCENTRATIONS OF 6-OXO-PROSTAGLANDIN F1\g=a\AND THROMBOXANE B2 IN THE TRACHEAL FLUID OF FOETAL SHEEP

Prostaglandins of the E and F series have been shown to relax or contract respectively guinea-pig trachea and recently it has been demonstrated that the prostaglandin endo-peroxides PGG2 and PGH2 (immediate precursors of prostaglandins E and F) have far greater potency in contracting tracheal smooth muscle than prostaglandin F (Hamberg, Svensson, Hedqvist, Strandberg & Samuelsson, 1976). Furthermore, both thromboxane A2 and prostacyclin can also elicit contraction of the trachea with thromboxane A2 being considerably more active (Omini, Moncada & Vane, 1977; Svensson, Strandberg, Tuvemo & Hamberg, 1977). Administration of thromboxane A2 has been shown to raise the tracheal insufflation pressure in guinea-pigs (Svensson et al. 1977) and indeed its stable metabolite thromboxane B2 is released in relatively large amounts from sensitized guinea-pig lungs when challenged with antigen (Dawson, Boot, Cockerill, Mallen & Osborne, 1976; Hamberg et al. 1976). Prostaglandins are also known to exert profound effects on the ductus arteriosu