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TESTICULAR ANDROGEN AND OESTROGEN LEVELS DURING THE POSTNATAL PERIOD IN RAMS

Summary.: Testosterone, androstenedione, oestrone and oestradiol-17β were determined in testes of Île de France rams from birth to 4 years of age. Steroid levels were measured by micromethods using gas-liquid chromatography with electron capture detection.

The major androgen of both the adult and early postnatal testes was testosterone. During the first 24 hr after birth, testosterone levels were not lower than 10 ng for both testes. With increasing age, there was a decline in testosterone concentration which lasted until the age of 20 days. From Day 25, testosterone in testis tissue increased and reached a value of 5·5 µg for both testes by the 7th month. During adulthood, testicular testosterone reached a concentration as high as 28 µg for both testes.

The ratio of androstenedione to testosterone in testicular tissue varied from 0·05 to 0·26 during the first 24 hr after birth, from 0·27 to 0·90 during the period from 2 to 20 days of age and from 0·12 to 0·60 in animals older than 20 days.

Detectable amounts of oestrone and oestradiol-17β could be found in the testes of lambs removed during the first 4 hr after birth and in the testes of animals older than 20 days.