Cytotoxicity of some indium radiopharmaceuticals in mouse testes

The biological effects of [111In]oxine, [111In]citrate, and [114mIn]citrate localized in mouse testes as well as the effects of external x-rays are investigated. The in vivo radiotoxicity of [111In] oxine is far greater than the chemotoxicity of oxine. Of these radiolabeled compounds, [111In] oxine is the most effective in reducing the sperm-head population, the mean lethal dose (D37) to the organ being about 0.16 Gy at 37% survival of the sperm heads. The corresponding values of D37 for [111In]citrate, [114mIn]citrate and x-rays are approximately 0.34, 0.57, and 0.67 Gy, respectively. The present results affirm our earlier finding of the inadequacy of conventional dosimetry in estimating the biologic consequences of Auger-electron emitters in vivo. The very different radiotoxicities of [111In]oxine and [111In]citrate draw attention to the role of the chemical nature of the radiolabeled compounds in the expression of biologic effects in vivo, an aspect that is not considered explicitly in the formulation of conventional dosimetry.