Cumulative labeling of embryonic mouse neural retina with bromodeoxyuridine supplied by an osmotic minipump

I describe a method for providing cumulative label of bromodeoxyuridine (BrdU) to mouse embryos. Commercially available osmotic pumps, which release their contents at a steady rate, were implanted subcutaneously in the interscapular space of pregnant mice on embryonic day (E) 9.5-12.5. Survival times varied from 4h to 37 days. Tissues (embryonic and neonatal eyes and maternal intestine) were immunochemically labeled for BrdU and examined histologically. The first detectably labeled cells appeared 4-7h post-implantation (hpi) and all cycling cells were labeled for at least 7 days post-implantation (dpi). Retinal development appeared normal. Terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling (TUNEL) stained retinas that had been exposed to BrdU showed no more apoptotic cells than those unexposed. I conclude that the maternally implanted osmotic pump successfully provides cumulative BrdU labeling in the mouse embryo.