Protection of Lymphocytes in the Thymus of X-irradiated Rats by Cysteamine

Abstract

CYSTEAMINE and cystamine have been reported to be ineffective in preventing the early pycnotic degeneration of lymphocytes in the thymus of X-irradiated rats¹. This finding appears to be inconsistent with the known radio-protective action of sulphydryl agents against killing of these cells in vitro^1–4, and against radiation-induced changes in the weight and enzymatic activities of thymus in vivo^5–8. The negative report was based on experiments in which a relatively low dose of X-rays (300 r.), and smear preparations, were used. Since smear preparations would tend to mix the radio-sensitive lymphocytes of the cortex with the lymphocytes of the medulla, which are radio-resistant in situ^9,10, we have investigated the effect of cysteamine on the thymus using both tissue sections and smeared cell suspensions. In addition, a range of radiation exposures (200–3,000 r.) have been used. The present study shows that cysteamine does have a protective effect against the early radiation-induced pycnosis in thymus, particularly among the radio-sensitive lymphocytes of the cortex.