A COMPREHENSIVE PROTOCOL FOR CONDUCTING THE SYRIAN-HAMSTER EMBRYO CELL-TRANSFORMATION ASSAY AT PH 6.70

Studies from our laboratory have demonstrated several advantages of co nducting the Syrian hamster embryo (SHE) cell transformation assay at pH 6.70 compared to that done historically at higher pH values (7.10-7 .35). These include reduction of the influence of SHE cell isolates an d fetal bovine serum lot variability on the assay, an increase in the frequency of chemically induced morphological transformation (MT) comp ared to controls, and an increased ease in scoring the MT phenotype. T he purpose of this paper is to report a comprehensive protocol for con duct of the pH 6.70 SHE transformation assay including experimental pr ocedures, a description of criteria for an acceptable assay and statis tical procedures for establishing treatment-related effects. We have a lso identified several assay parameters in addition to pH which can af fect transformation frequencies, particularly the critical role colony number per plate can have on transformation frequency. Control of thi s parameter, for which details are provided, can greatly increase the reproducibility and predictive value of the assay.