Developmental Patterns of Plasma and Testicular Testosterone in Rabbits from Birth to 90 Days of Age

Abstract

Testosterone was measured every 10 days in plasma and testes of male rabbits, from birth to 90 days of age. Plasma testosterone varied little from birth (3.8 ng/10 ml) to 40 days (4.6 ng/10 ml) and increased thereafter until the 60th day (40.1 ng/10 ml). This level, characteristic of puberty, remained unchanged until the 90th day and decreased thereafter. Testicular testosterone content followed a similar pattern. It remained steady from the 1st to the 20th day. From the 20th day to the 50th day it rose slowly. Between the 50th and 60th day it increased rapidly and reached its maximum at the 60th day (339.8 ng). It remained at the same level until the 90th day. Testicular testosterone concentration was steady from 1 to 20 days, then increased quickly, reaching a maximum at 60 days (154.8 ng/100 mg). It then decreased until the 90th day (48.4 ng/100 mg).