DEVELOPMENT OF TYROSINE-HYDROXYLASE ACTIVITY IN DISSOCIATED CEREBRAL CELL-CULTURES

The present study describes the development of tyrosine hydroxylase (TH) activity in dissociated cerebral cell cultures. Cerebral hemispheres from 8-day-old chick embryos were mechanically dissociated and grown in culture for periods of up to 30 days. Levels of TH activity were low throughout the first 2 weeks in culture, then rose sharply, increasing ten-fold during the third and fourth week in culture. This maturational profile was similar to that seen in vivo, where TH activity in cerebral hemispheres was negligible until fourteen days of embryonic age, then increased fivefold during the last week of embryonic development. Tyrosine hydroxylase activity in cultured cerebral cells was significantly higher than TH activity in the same tissue under in vivo conditions. This observation suggests the participation of factors unique to the culture system, perhaps related to serum or other components of the growth medium, in the enhancement of TH activity in vitro.