The inhibitory effect of aspirin on lymphatic contractility

Spontaneous contractions and those elicited by two different methods of electrical stimulation were studied in isolated segments of bovine mesenteric lymphatic vessels. The effect of aspirin (a cyclo-oxygenase inhibitor) on spontaneous and evoked contractions of isolated lymphatic vessels was investigated. Aspirin at doses of 10(-6) M or greater depressed both spontaneous and action potential-dependent evoked contractions, but failed to inhibit contractions evoked by high current field stimulation. These latter contractions were rapidly depressed by the application of D600. When aspirin was applied for five minute periods, inhibition never occurred within the period of drug administration but was delayed, with maximum inhibition occurring approximately 10 min after washout of the drug. It is concluded that the inhibitory action of aspirin is unlikely to be a non-specific depression of the contractile mechanism, but rather a reduction in excitability probably as a result of cyclo-oxygenase inhibition.