T. Randall Wrenn

Effect of several dietary levels of o,p′-DDT on reproduction and lactation in the rat

ConclusionsThe levels of o,p′-DDT fed in this experiment were considerably above those likely to be encountered in accidental feed adulteration or through careless use of the insecticide. Even though these experiments included the critical periods of reproductive maturation and were extended through two pregnancies, no adverse effect on female reproduction could be determined. Since o,p′-DDT is the most estrogenically potent of the isomers or metabolic analogs of DDT, these experiments serve to indicate levels of exposure that can be safely tolerated throughout growth, pregnancy, and lactation. Further, since technical DDT contains only 15–20% of the o,p′-isomer, by extrapolation it would be expected that daily amounts as high as 1 gram of the technical insecticide preparation (80–85%, p,p′-DDT) could be ingested without deleterious effects on reproduction, except for the physiological effects of so large a dose.As judged from these experiments on a small laboratory rodent, our results indicate that o,p′-DDT, an estrogenically active pesticide, does not adversely affect reproduction in mammals.

Antifertility action of IUDs inserted in rats after mating

Abstract Monofilament nylon, double S-shaped IUDs were inserted through the cervical os into one uterine horn of rats on days 1–6 following mating. Other rats were similarly treated with sham insertions. Examination of uteri on day 18, 19 or 20 following mating revealed that placement of an IUD was contraceptively effective on all days through day 5, the time implantation normally occurs. The procedure was least effective in preventing implantation when inserted on day 1. The insertion of the empty applicator did not cause reduction in the number of pregnancies if inserted early in gestation, but caused reduction in the number of horns containing pregnancies on days 4 and 5. Both horns receiving IUDs and sham treatments on days 4 and 5 showed a high incidence of deciduoma development. Untreated contralateral control horns in both series, IUD and sham insertions, had equal numbers of live fetuses at 18–20 days, indicating that the IUD did not increase embryonic death in these horns. The experiment provides evidence that IUD action to prevent implantation requires only 2 days at most to become effective.