5 '-deiodinase activity in cultured glial and fibroblastic cells from the cerebella of newborn rats

The cerebellum of young rats contains significant 5'-deiodinase (5'-D) acti vity, but technical difficulties have made it impossible to identify the en zyme in cultured cerebellar astrocytes. We have developed a culture method which allows cerebellar astrocytes from 6-day-old rats to grow and develop 5'-D activity. Astrocytes cultured for 2 weeks in medium containing 3.25 mu M reduced glutathione (GSH) and 0.21 mu M vitamin E (VitE) as alpha-tocoph erol had 5'-D activity which was stimulated by 1 mM dibutyryl cyclic adenos ine monophosphate (dBcAMP) given 16 hours before measuring enzyme activity. Cells cultured without GSH and VitE showed little 5'-D activity, which was not stimulated by dBcAMP. Primary cultures of cerebellar astrocytes were c ultured for four weeks with or without GSH + VitE, and stimulated by dBcAMP had high 5'-D activity, but were also sometimes contaminated with fibrobla sts. The effect of such contamination on the astrocyte 5'-D activity was as sessed by preparing primary cultures of fibroblasts from the meninges surro unding 6-day-old rat cerebella. They were grown in the same media and under the same conditions as the astrocytes. The cultured fibroblasts had 5'-D a ctivity independent of GSH + VitE or culture time. The 5'-D activity of bot h cell populations could be type II 5'-deiodinase (5'-DII) because it was n ot inhibited by 6-n-propylthiouracil (PTU). Thus, cerebellar astrocytes cul tured for 2 weeks in medium containing GSH and VitE have 5'-DII activity. P rolonged cultures favor enzyme activity, but also enhance contamination wit h fibroblasts, which may also show 5'-DII activity.