PSK, a biological response modifier, induces a systemic developmental delay in X-ray irradiated mouse embryos : coincidence with its anti-teratogenic effect

Some biological response modifiers (BRMs) have been shown to suppress teratogenesis. We previously showed that PSK, a BRM and a protein-bound polysaccharide extracted from Basidiomycetes, suppressed X-irradiation-induced ocular anomalies in mouse embryos.
In those studies, we noticed that the irradiated and PSK-treated embryos tended to be smaller in body size than the controls that were irradiated but not treated with PSK, in spite of the reduced teratogenesis. In this study, therefore, we analyzed in detail systemic development from embryonic day (E)7.75 to E9.0 of embryos that were irradiated and treated with PSK at E7.5, following the same experimental protocol used in the previous study. PSK treatment not only enhanced the X-irradiationinduced developmental delay, but also delayed development, albeit less extensively, as compared with controls. These developmentally delayed embryos generally showed proportional and symmetric size reduction. Possible mechanisms of the PSK-induced delay in systemic development and a relation with its anti-teratogenic effect are discussed.