Effect of Ionizing Radiation on Uterine Contractility

Abstract

INVESTIGATIONS of the effects of ionizing radiation on the nervous system and neuromuscular responses reveal a greater variation in the degree of radiosensitivity than is shown by almost any other mammalian tissue. Earlier observations on macroscopic and histological damage occurring only after supra-lethal doses^1,2 have to be viewed in the light of more recent work on functional changes occurring after very low doses and in the absence of visible damage³. It is also striking that the greatest changes seen with low doses have been demonstrated in smooth muscle responses as against striated muscle and its nerve-muscle preparations. Delay in gastric emptying time has been demonstrated with as little as 25 rads⁴, and Hug⁵ has shown that 25 rads will induce alterations in the contraction of nerve muscle preparation set up from the leech and the earthworm. Whether these last two observations are the result of stimulation of muscle or of nerve is not clear, and irradiation of muscle alone has generally shown considerable resistance to damage⁶. The response of smooth muscle to humoral agents such as oxytocin can be regarded as a measure of muscle sensitivity and, if the observations are carried out in vitro, largely unaffected by nerve stimulus. The radiosensitivity of uterine muscle to commercial preparations of oxytocin has therefore been investigated, and a marked increase in responsiveness demonstrated after mid-lethal doses of X-irradiation.