Increased production of PGI2-like activity by frozen-thawed rat aorta

The effects of storage conditions, temperature, and time on the ability of the rat thoracic aorta to produce a platelet aggregation inhibitor were investigated. Aortic fragments were incubated in Tris buffer, aliquots of which were then tested for their ability to inhibit ADP-induced human platelet aggregation. The incubation fluid of samples that had been soaked in Tris buffer at 4 degrees C for 24 hours contained no inhibitor activity, whereas the incubation fluid of similar samples that had been kept at 4 degrees C but not soaked in buffer contained comparable inhibitor activity as that of fresh samples. The incubation fluid of samples that had been kept at -20 degrees C or -80 degrees C contained greater inhibitor activity than that of fresh samples, and was maintained in -20 degrees C samples for 7 days, and -80 degrees samples for 28 days. The aortic inhibitor had similar properties as PGI2.