Thyrotropin regulation of plasminogen activator activity in primary cultures of ovine thyroid cells

In primary cultures of ovine thyroid cells, a high level of plasminogen activator (PA) activity was detected in the culture media. This level is much higher than in primary cultures of Sertoli cells, granulosa cells, and pituitary cells. PA activity increased with time in culture and was regulated by TSH and insulin. Activity gel analysis of the culture media revealed a major band of 43,000 daltons and a minor one of 70,000 daltons, suggesting the presence of both of the urokinase-type and the tissue-type PA in the media.