[Mesothelioma in rats following-intrapleural-injection of crocidolite]

In order to investigate the potential of pleural mesothelioma induced by crocidolite, author collected samples from four county areas (Dayao, Yaoan, Muding and Yanyuan) in China. A suspension of 1 ml containing 20 mg crocidolite fiber was injected into the right pleural cavity of each rat in various test groups and UICC crocidolite group, totally 40 mg. The negative control was given saline. The results showed that the incidence of mesothelioma was 56.0%-68.8% (in which the rate of induction in Yanyuan group was the highest), and the survival time of the first case of mesothelioma was 273-347 days in the test groups, the Yanyuan group had shorter latency, and the mean survival days of the rats with mesothelioma for four groups were 560, 490, 593 and 498 days respectively; the shortest mean survival time was that for Yanyuan group. The major histological type of mesothelioma induced by crocidolite was the fibrous type. The degree of differentiation in all mesotheliomas was mainly intermediate and low. The results suggested that when rats were intrapleurally inoculated with samples of crocidolite and saline, an appreciable proportion of animals developed mesothelioma except those of the saline group. Compared with other groups, the Yanyuan group had stronger potential of crocidolite-induced mesothelioma.