In vitro Reinitiation of Pituitary Somatotropin Release by an Acid Extract of Hypothalamus. ∗ †

Summary

Two groups of rat anterior pituitaries were cultured on synthetic medium 199 at 35°C in an atmosphere of 95% O₂-5% CO₂ for 9 days. The medium was changed every 3 days. At the end of the 9-day culture period, the medium from each 3-day period was assayed for growth hormone by the standard tibia test. Both groups of anterior pituitaries released substantial amounts of growth hormone during the first 3 days of culture, but no significant amounts during the second or third 3 days of culture. Addition of a rat hypothalamic extract at the beginning of the third 3 days of culture, reinitiated growth hormone release to 78%