| Popis: |
Large groups of Sprague-Dawley rats were given either small single intravenous injections of 0.75, 0.5, or 0.25 microcurie of Po/sup 210/ per kilogram body weight; or repeated doses designed to maintain a relatively constant polonium burden of 0.01 microcurie per kilogram body weight. Since the most sensitive criteria of polonium damage had been shown to be shortening of life span, or possibly increased tumor incidence, these two possible effects were given the most attention in observations continuing throughout the adult life of the animals. Definite shortening of life span occurred in male rats that had received the single doses of 0.75 or 0.5 microcurie per kiiogram body weight. Life span shortening at the 0.25 microcurie level was not as definite, though probable. None of the groups of females receiving single doses showed significant life span shortening, possibly in part because of the greater variance of the female populations. A maintained polonium burden of 0.01 microcurie per kilogram body weight was completely without measurable effect. No effect on tumor incidence was observed in any of the single or multiple dose groups. However, the tumor incidence in all groups of old injected and control rats was very high. (auth) |
