To study the paternal effect, particularly of accessory sex gland secretions, on DNA synthesis in golden hamster zygotes, the glands were surgically removed from golden hamsters resulting in 4 groups: SH, sham-operated; AGX, bilateral excision of ampullary glands; VPX, bilateral excision of ventral prostates; and TX, excision of all accessory sex glands. Each female was mated with one male and killed at 6, 8, 10, or 12 h postcoitus (p.c.). Embryos were collected, and zygotes in S-phase were identified by immunocytochemical techniques after pulse-labeling with 50 microM 5-bromo-2'-deoxyuridine-5'-monophosphate (BrdU) in Tyrode's albumin lactate pyruvate medium for 30 min. In another experiment, embryos at 6 h p.c. were incubated in 50 microM BrdU for 6 h. Presumptive zygotes were stained with propidium iodide to visualize pronuclei. The BrdU pulse-labeling results showed that the percentages of embryos with 1 or 2 pronuclei in S-phase at 8 h p.c. in VPX (44.3 +/- 10.4) and TX (41.6 +/- 10.6) groups were significantly lower (p < 0.05) than that in the SH group (69.0 +/- 5.5). In the AGX group, although the percentage of embryos with 1 or 2 pronuclei in S-phase was not significantly different from that of the SH group, the percentage of 8-h embryos with 2 pronuclei in S-phase was 51.6 +/- 2.8, significantly lower than in the SH control (68.1 +/- 6.0, p < 0.05). When the embryos were labeled with BrdU for 6 h, the percentages of embryos with 1 or 2 pronuclei in S-phase were not different among the 4 groups. However, the percentage of embryos showing 2 pronuclei in S-phase was significantly lower in the AGX group (78.4 +/- 6.7) than in the SH group (91.8 +/- 2.9, p < 0.05). These results suggest that accessory sex glands can affect DNA synthesis in hamster zygotes and that the mechanisms by which ampullary gland and ventral prostrate secretions affect the first cell cycle are probably different. A significantly higher incidence (p < 0.001) of polyspermy was observed in embryos sired by males without ampullary glands (5.2 +/- 1.0%) compared with those sired by the SH group (0.8 +/- 0.3%).