Effects of age on cell proliferation in mouse duodenal crypts

Abstract

Using tritiated thymidine as a DNA label the generation times (GT) and durations of G 1, S, G 2 and M have been established for BCF 1 mice at 55, 100, 300, 400, 675, 825 and 1050 days of age. GT was shown to be almost 50 per cent longer in the 1050-day-old BCF 1 than in the 55-day-old animals. The increase in GT is, however, not gradually progressive, but takes place at the end of the growing period between 55–100 days and at the beginning of “senility” at around 825 days of age. The first change involves an increase in G 1 from 1·9 to 4·7 hr, while the change in the old animals is due to an increase in both S and G 1. The increase in GT in the old mice is accompanied by a pronounced decrease in the number of cells in the proliferative compartment.