CELL-CYCLE KINETICS IN RAT PROSTATIC EPITHELIA - NUCLEAR MIGRATION DURING G2 PHASE

Proliferative events in luminal epithelial cells of the rat ventral pr ostate were studied in 2 experiments. In experiment 1 a longitudinal s urvey of the rat prostate was conducted between 22 and 88 days of age. The pattern of temporal changes in the weight of the ventral prostate paralleled that of the testis, an observation consistent with the kno wledge that the prostate is an androgen target organ. However, the tot al number of mitotic cells per prostate showed a biphasic pattern of d istribution. The count was high (82 per prostate) in the prostate of 2 2-day-old rats and it decreased to a low value (25 per prostate) by ag e 30 days, a period corresponding to the onset of puberty in rats. The total mitotic count per prostate increased gradually and reached a pe ak (85 per prostate) around age 60 days when it started to decline gra dually despite a continuous increase in prostatic weight. In experimen t 2 cell cycle parameters of these cells were determined in young adul t rats (age 70 days or 250 gm. body weight) by an in vivo H-3-thymidin e pulse-chase approach. The apparent duration of various phases of the cell cycle was estimated as G1-11.5 hours, S-6.5 hours, G2-3.0 hours, M-2.0 hours and total cell cycle-23 hours. The fraction of cells in t he S phase was 2.1%, which was extrapolated to give rise to a total gr owth fraction of 7.4%. In addition, it was noted that there was a migr ation of the nucleus from the base toward the apex of the epithelial c ells during the G2 phase of the cell cycle in preparation for cell mit osis. Following mitosis nuclei of the 2 daughter cells returned to the usual basal position. These parameters will. be used as basis of our future kinetic studies in the rat prostate.