Background. Establishing glomerular basement membrane (GBM) thickness is important in the diagnosis of some renal diseases. It is widely believed that GBM thickness varies according to the processing method, yet there appear to be no published data to support this. In this study we aimed to determine whether the choice of intermediate solvent and embedding resin influenced the thickness of the GBM and to assess the magnitude of any such effect. Methods. Subcapsular renal cortical rat tissue was

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... processed for electron microscopy using four different intermediate solvents [propylene oxide (PO), xylene (Xyl), acetone (Ac) or ethanol (Et)], and three epoxy resins [Araldite (Aral), TAAB embedding resin (TER) or TAAB low viscosity resin (TLV)]. GBM thickness was estimated by the orthogonal intercept method. Results. Compared with PO-Aral embedding, GBM was significantly thinner in Xyl-Aral, Ac-Aral and Xyl-TER, and significantly thicker in PO-TER-, Ac-TER-, Et-TERand PO-TLV-embedded tissue (P < 0.05 in all cases). No significant difference was seen with Xyl-TLV-and Ac-TLVembedded tissue. Et-Aral and Et-TLV embedding resulted in poor quality blocks. Conclusions. The results suggest that the choice of both intermediate solvent and resin influences shrinkage of the GBM during TEM processing.