On the stability of DNA in photoreceptor cells of rat retina.

DNA turnover in post-mitotic photoreceptor cells of F344 rat retina was investigated. Developing retinas of newborn rats were labelled by multiple injections of (methyl-3H)thymidine. One eye was removed on day 60 and embedded in paraffin. The groups of rats were killed 180, 365, 540 or 730 days later and the second eye was removed. Autoradiographic studies on pairs of eyes showed no detectable DNA turnover in photoreceptor cells up to the end of the experiment (near median life-span, 50% survival age). The DNA of these photoreceptor cells is not replaced through the life span of the animals; the results thus suggest that it is very stable and possibly protected in a specific manner.