DURATION OF THE CYCLE OF THE SEMINIFEROUS EPITHELIUM, ESTIMATED BY THE 5-BROMODEOXYURIDINE TECHNIQUE, IN LABORATORY AND FERAL RATS

The stability of the duration of the cycle of the seminiferous epithel ium was determined by investigating incorporation of 5-bromodeoxyuridi ne into S-phase germ cells of normal and hemicastrated standard labora tory rats (Sprague-Dawley) and feral Brown/Norway rats Rattus norvegic us). Feral rats were trapped on farms in the surroundings of Munster. The duration of the cycle of the seminiferous epithelium, determined a t intervals of 12 days (3 h versus 12 days 3 h after 5-bromodeoxyuridi ne injection), was remarkably constant and similar in intact laborator y rats (12.49 +/- 0.05 days, n = 13, mean +/- SEM) and feral rats (12. 44 +/- 0.06 days, n = 8). In hemicastrated laboratory and feral rats t he duration of the cycle was similar to that in intact animals, indica ting that hemicastration did not influence the kinetics of the seminif erous epithelium cycle. However, the coefficients of variation of the estimated duration of the cycle of the seminiferous epithelium were at least three times lower in hemicastrated rats (one testis from the sa me animal serving as reference point) compared with that of intact rat s (the reference point based on the average staining frequency at 3 h) . Overall, no significant differences between laboratory and feral rat s could be observed with regard to testis weight and serum concentrati ons of FSH and testosterone. The number of cells per testis, determine d by flow cytometry, was similar in laboratory and feral rats, except for a slight but significant difference in the haploid:tetraploid cell ratio (6.3 +/- 0.2 versus 7.5 +/- 0.3, P < 0.05). It is concluded tha t the duration of the cycle of the seminiferous epithelium is identica l in feral Brown/Norway rats and their descendent laboratory rat strai n, Sprague-Dawley rats. Hemicastration (each animal being its own refe rence point) profoundly increased the precision of the determination o f duration of the cycle of the seminiferous epithelium, at least for t he duration of one cycle.