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A new model, whose purpose is the quantitative study of the corelation between the force of contraction of a platelet aggregate and morphological, biochemical or pharmacological parameter is described. This preparation is made by centrifuging cold recalcified PRP over a sheer nylon, elastic mesh kept stretched in a hoop inside a specially made centrifuge tube with a solid flat bottom. As a result, the mesh becomes impaled in the flat platelet pellet giving it structural support. The supernatant PPP is decanted and the pellet washed with cold Tyrodes solution to eliminate as much residual plasma as possible. Reheating the preparation at 37° activates the aggregation of the platelets and the coagulation of the residual fibrinogen. The final result is a disc of approximately .3mm thickness with a density 7-8 × 107 plat./mm3. The disc is disassembled, cut in strips which are hung using classical techniques of vascular smooth muscle in a bath, where the force produced by its contraction can be measured either isotonically or isometrically. Forces up to 500-700 mg per strip are produced at maximal contraction. The behavior of the preparation can be followed for periods of up to 5 hours. Under the effect of drugs it shows reversible contraction-relaxation cycles in an all or none mode. Kcontraction for epinephrine was 10-8M; nor-epinephrine, 10-7M. Krelaxtaction for PGE1 was 10-9M: sodium nitroprusside, 10-8M: (+)propranolol, 10-6M; phentolamine, 10-4M. It also shows reversible, ultraviolet-induced photorelaxation when excited at 366 nm. Similarities with aortic vascular smooth muscle and morphological characteristics will be discussed.

The Platelet Strip: A New Model for the Study of the Mechanochemical Properties of a Platelet Aggregate