The effect of a single lethal x-irradiation exposure on the activity of lipoprotein lipase in the tissues of the rat.

Wistar male rats, both fed and fasting for 16 h prior to irradiation, were exposed to a single lethal X-ray dose of 387 mC X kg-1 (1 500R). The activity of lipoprotein lipase in white adipose (epididymal) tissue and heart muscle and the concentration of serum triglycerides were determined at 1, 6, 24, 48, and 72 h after radiation exposure. In the early time periods, at 1 and 6 h after exposure, the activity of lipoprotein lipase was decreased in adipose tissue and increased in heart muscle of the irradiated fed rats; in fasting rats it was decreased in heart muscle at 1 h after exposure. The concentration of serum triglycerides was increased at 1 h and decreased at 6 h after exposure in fed rats. In these rats, alterations in serum triglycerides correlated with changes in lipoprotein lipase activity in adipose tissue. Alterations observed at the later time periods were more dependent on the time interval between radiation exposure and the analysis. Lipoprotein lipase activity increased with time after radiation exposure up to the maximal values at 72 h. Fasting prior to and after irradiation substantially modified the response of animals to radiation.