Abstract:An acute toxicity assay of cadmium were performed using bullfrog as the material. The concentrations of Cd ²⁺are 0.0, 0.5, 1.0, 2.0, 4.0 mg / L respectively either with distilled water(exposure agent I)or Dendrobium officinale extracts(exposure agent II). The mutagenic effect to the bullfrog erythrocytes under the stress of the exposure agent I or exposure agent II were determined. The results showed that with the concentration of Cd ²⁺increase in exposure agent I, ratios of micronuclei, apoptosis and abnormal nuclei of the bullfrog erythrocytes firstly increase and then decrease as a parabolic curve. Peaks of these ratios were reached at concentration of Cd ²⁺2.0, 2.0 and 1.0 mg/L respectively. Exposure agent II showed similar trend while ratios mentioned above reached maximal all at concentration of Cd ²⁺2.0 mg/L. Dose effect between the Cd ²⁺concentration and the ratio of apoptotic cells or micronuclei was observed. In addition, exposure agent II revealed less toxicity compared with exposure agent I in terms of micronuclei, apoptosis and abnormal nuclei ratios of the bullfrog erythrocytes. Therefore, Dendrobium officinale has protection effect over heavy metal stress such as Cd ²⁺on bullfrog erythrocytes.