Abstract
The action of prostaglandin F2a (PGF2a)1 on guinea-pig isolated trachea has been studied. Special emphasis was placed on considerations of the possible beta-adrenergic blocking activities of this essential fatty-acid derivative. | Experiments were performed using a 20 ml tissue bath and a modified phosphate-Tyrode solution. Measurements were made by an isotonic myograph and displayed on a Physiograph recorder. | Cumulative log dose-response curves to isoproterenol before and after either PGF2a or a beta blocker (MJ 1999) provided data for calculating and plotting both isoboles and Lineweaver-Burk curves. These, calculations indicated that PGF2a is not inhibitory to the action of isoproterenol on guinea-pig trachea in vitro. | Further experiments demonstrated that PGF2a possesses a weak inhibitory activity on methacholine-induced tracheal tone. That this inhibitory activity is not mediated through the beta- adrenergic receptor was shown in experiments where beta blocker (MJ 1999) failed to inhibit the activity of PGF2a. Inhibition of methacholine-induced tone by PGF2a was further differentiated from that produced by isoproterenol on the basis of observations that PGF2a-induced inhibition was incomplete, even at the highest concentrations.