Endothelial alkaline phosphatase activity loss as an early stage in the development of radiation-induced heart disease in rats.

Alkaline phosphatase activity of capillary endothelial cells in the heart of Wistar and Sprague-Dawley rats was studied sequentially after single doses of 10, 15, 20, or 25 Gy. Following irradiation capillary density and alkaline phosphatase activity were focally lost before myocardial degeneration or clinical symptoms of heart disease developed. Recovery from both changes took place after doses of 10 or 15 Gy. The decrease in capillary density and enzyme activity showed the same strain difference in latency times and in the extent of the lesions as previously described for pathological and clinical signs of heart disease.