Developmental expression and distribution of amphibian glutathione transferases.

This work is aimed at detecting the expression and location of embryonic Bufo bufo GST (bbGSTP1-1) and adult B. bufo GST (bbGSTP2-2) during toad development, in order to assign a putative role to these enzymes also on the basis of their compartmentalization and to verify whether during the premetamorphic liver ontogeny the bbGSTP2-2 form appears. This study was also performed in the adult liver (the primary site of Pi class GST expression) and in the mature ovary, to discern if the embryonic form derives from maternal form. The results show that the embryos and the ovary express only bbGSTP1-1. Moreover, bbGSTP1-1 distribution is the same both in the early embryos and in the ovary: this strongly suggests that bbGSTP1-1 is of maternal origin. As development goes on, a wide distribution of bbGSTP1-1 all over the differentiating organs is observed. The embryonic liver expresses exclusively the bbGSTP1-1 form, while the adult liver is highly positive only towards the bbGSTP2-2 form. This implies that the switch towards the adult bbGSTP2-2 form occurs in metamorphic or postmetamorphic phases and that the detoxication metabolic requirements of the embryo may be completely fulfilled by the bbGSTP1-1 isoenzyme.