I am new to performing hepatic uptake assays. I have to optimize uptake of estrone-3-sulfate through oil-spin method. The time points we are testing initially are from 30sec through 180sec with initial concentration of 1uM (as active uptake is predominant at lower concentrations). Optimization has to be done using radioactive compound (analyzed by LSC) and non-radiolabeled compound (analyzed by LC/MS). 

As the time points are short and I am new with this technique, can you please share your experiences and/or give valuable suggestions that might help me to perform and optimize the assay better?