Effect of nicotine on prostacyclin formation in human endocardium in vitro

1. 1. The effect of nicotine on the formation of prostacyclin by human endocardium was studied in vitro. 2. 2. Slices of cardiac valve cusps were incubated in a saline medium and the prostacyclin-like activity generated spontaneously by the tissue specimens was assessed in terms of its capacity to inhibit ex vivo platelet aggregation. 3. 3. In separate experiments supernatants of valvular tissue homogenates were incubated with [ 14C]arachidonate. 4. 4. This resulted in the appearance of labelled 6-keto-prostaglandin F 1α in the radiochromatograms, indicating the formation of prostacyclin in the homogenates. 5. 5. Nicotine inhibited dose-dependently the spontaneous generation of prostacyclin-like activity (I 50 ≈ 2 × 10 −4M), as well as the formation of 6-keto-prostaglandin F 1α (I 50 ≈ 2 × 10 −5M), in inhibitory effect of the drug on endocardial prostacyclin production.