Prostacyclin and thromboxane release from the vessel wall--comparison between an incubation and a perfusion model

Prostacyclin (measured as its stable degradation product 6-keto-PGF1 alpha) and thromboxane (measured as its stable degradation product TxB2) produced by the vascular wall were measured by radioimmunoassay (RIA). Four pieces from the rabbit aorta and four from the caval vein were used. One piece was incubated in Hank's balanced salt solution (HBSS), one piece with additional indomethacin, and the other pieces were mounted in a perfusion system so that only the endothelium was exposed to the buffer solution with or without indomethacin. There was a higher release in the piece incubated in the buffer than in the piece which was perfused, indicating that not only the endothelium releases prostacyclin and thromboxane from the vascular wall. The 6-keto-PGF1 alpha/TxB2 ratio was higher in the perfused than in the incubated samples suggesting that 6-keto-PGF1 alpha release is higher in the endothelium than in the other wall layers and/or that TxB2 production is higher in the outer layers than in the inner layers. No correlation was found between the release from the incubated vessel and from the perfused vessel. There was a higher release of 6-keto-PGF1 alpha from aortas than from caval veins, when incubated or perfused, whereas there was a tendency to a higher release of TxB2 from veins than aortas.