Experimental thrombocytopenia and capillary ultrastructure.

By David Shepro, H. E. Sweetman, and H. B. Hechtman R EDUCED circulating platelets or thrombocytopenia is associated frequently with a propensity for petechial and purpuric hemorrhages. This observation has led to the concept that platelets support vascular endothelium and maintain vascular integrity by a mechanism separate from hemostasis or vascular repair. ‘ 6 Experimental thrombocytopenic animal models have been used to investigate vessel wall defects that might result from low platelet counts. However, electron microscopic studies of tissues from thrombocytopenic animals have not shown any apparent ultrastructural changes in the microvascular endothelium or microvessel wall,7’#{176} with one exception: tongue skeletal muscle capillaries that are normally nonfenestrated and continuous were reported to be fenestrated and attenuated in experimental thrombocytopenic rabbits.’ 1.12 The purpose of the present investigation was to examine tongue skeletal muscle capillaries in control and thrombocytopenic mice and hamsters to determine if attenuation and fenestration of skeletal muscle capillaries are characteristic of a thrombocytopenic state in these animals. In addition to skeletal muscle capillaries, several other tissues were examined for ultrastructural changes in capillary endothelium associated with thrombocytopenia. Our data show no ultrastructural differences in capillaries in any of the tissues examined between control and thrombocytopenic hamsters and rats.