Changes in uptake of 3H-progesterone by female rat brain and pituitary from birth to sexual maturity.

3H-progesterone uptake by various parts of the brain, pituitary and skeletal muscle was compared in newborn, 5-, 10-, 15-, 20-, 25- and 50-day old female rats at 1 hr after a single intraperitoneal injection of 50 muCi/100g body weight. High uptake values in newborn animals and in those aged 5 days were found in all tissues investigated. A sharp decrease in accumulation was observed from birth and/or 5th day of life.