Effects of labetalol on the arachidonic acid metabolism in human blood platelets, and in lung and aorta of the rat.

Effects of labetalol on the arachidonic acid metabolism in washed human blood platelets, and in lung and aorta of the rat was studied. Effects of this drug on the aggregation induced by usual aggregation agents, and on the prostacyclin generating capacity of rat aorta as assessed by its antiaggregation effect were also studied. The following results were obtained. 1. Reduced generation of thromboxane and HHT in platelets was observed at 1 mM conc. of the drug. 2. This drug inhibited ADP-, collagen-, and epinephrine-induced aggregation in a dose dependent manner. 3. Arachidonate-induced aggregation was only slightly inhibited at 1 mM conc. of labetalol. 4. Aorta and lung synthesized more prostacyclin in its presence from exogenous labelled arachidonate. 5. Aorta synthesized more prostacyclin from its endogenous AA pool in the presence of labetalol as assessed by inhibition of platelet aggregation.