Increased vascularity of brain, heart, and skeletal muscle of polycythemic rats.

MILLER, A. T., JR., AND D. M. HALE. Increased vascularity of brain, heart, and skeletal muscle of polycythemic rats, Am. J. Physiol 2 1 g(3) : 702-704. 1970.-The vascularity of the cerebral cortex, right and left ventricle, and gastrocnemius muscle was measured in rats exposed to a simulated altitude of 18,000 ft, or injected ,daily with cobalt chloride, or transfused twice weekly with erythrocyte suspensions. Highly significant increases in vascularity of the cerebral cortex, left ventricle, and gastrocnemius muscle were sobserved in all three groups of animals. Vascular&y of the right ventricle was increased in altitude-exposed, but not in cobalttreated or transfused animals. The increase in vascularity was proportional to the increase in hematocrit in cerebral cortex and gastrocnemius muscle in all three groups of animals. In both right and left ventricle, the increase in vascularity relative to the increase in hematocrit was greater in altitude-exposed animals than in cobalt-treated or transfused animals. The nature of the stimulus responsible for the vascular changes has not been identified; it is suggested that increased blood volume or blood viscosity, as well as tissue hypoxia, may be involved.