DESAGGREGATION BY VERAPAMIL, SODIUM-NITROPRUSSIDE AND PGE(1), OF RABBIT PLATELETS AGGREGATED BY PAF-ACETHER - A MORPHOLOGICAL AND BIOCHEMICAL-STUDY

The action of sodium nitroprusside, an activator of guanylate cyclase, on rabbit platelets stimulated with PAF-acether, was studied singly o r in combination with verapamil. Not only did sodium nitroprusside in the range 10(-6) to 10(-4) M inhibit PAF-acether induced aggregation, but it also brought about desaggregation of previously aggregated plat elets, as also did verapamil. The results were compared with those obt ained with PGE1, when used alone and in combination with verapamil. Mo rphological studies were carried out on control and aggregated platele ts, and on platelets treated with verapamil either to inhibit aggregat ion or to bring about desaggregation. The platelets that had been desa ggregated by verapamil were discoid in shape, had very few pseudopodia and exhibited a near normal internal morphology, except that the open canalicular system was swollen and contained an electron dense materi al resembling the contents of the alpha granules. The morphology of pl atelets desaggregated by PGE, was similar to that of platelets desaggr egated by verapamil, including a swollen canalicular system containing electron dense material.