Effects of Prenatal and Postnatal Gamma Irradiation on the Rat Testis

Purpose: To determine the effect of acute irradiation during gestation and the neonatal period and of protracted exposure during the entire intra-uterine life on adult rat testis: influence of dose rate and threshold values.

Status: 1977 - 1988, terminated

Treatment: Acute and protracted Co-60 gamma irradiation: acute exposure to doses from 0 to 1.5 Gy at different dose rates on day 15 and 21 of gestation and day 0 and 2 of postnatal life.
A) Acute exposure to 1.5 Gy (dose rate 0.1 Gy/min) (sacrifice at an age of 3 months): Effect of intrauterine age
B) Protracted exposure during the entire intrauterine life (sacrifice at an age of 3 months): Effect of dose
C) Effect of dose rate for an exposure of 1 Gy to fetuses 16 or 21 days post conception (sacrifice at an age of 3 months).
D) Effect of low doses to determine threshold dose at a dose rate of 0.1 Gy/min, sacrificed at an age of 26 days

Dosimetry: Ionization chamber

Endpoints: Testis weight, histology and hormonal activity in prepueral and adult animals.

Animal: Sprague-Dawley SPF rats offspring

Results: A) Following exposure from day 18 post conception (p.c.) until day 2 post birth (p.b.), all germ cells in the testis were found to be killed and the animal was sterile,
B) A dose as small as 0.1 Gy/d resulted in a loss of all germ cells from the testis,
C) Nearly all germ cells were killed following an exposure to 1 Gy at a dose rate of 0.6 mGy/min on day 15 p.c.; at the other dose rates, the histology of the irradiated testis was similar to that of the control testis. After a dose of 1 Gy on day 21 p.c., all germ cells were killed and no effect of dose rate could be observed.
D) The threshold dose at which a decrease in germ cells could be detected is 0.2 Gy at days 18 p.c., 21 p.c. and the day of birth; it increases to 0.4 Gy on day 2 p.b.