RELEASE OF ALPHA-SUBUNIT OF GLYCOPROTEIN HORMONES FROM THE BULLFROG PITUITARY - POSSIBLE EFFECT OF ALPHA-SUBUNIT ON PROLACTIN CELL-FUNCTION

On the basis of our previous finding that prolactin (PRL) cells of the bullfrog (Rana catesbeiana) contain immunoreactive alpha-subunit of p ituitary glycoprotein hormones, experiments were conducted to see whet her the immunoreactive alpha-subunit is released from PRL cells. Cell immunoblot analysis revealed that approximately 10% of cells that rele ased immunoreactive PRL also released immunoreactive alpha-subunit. We stern blot analysis of the culture media revealed that a considerable amount of the free form of alpha-subunit was released from the dispers ed anterior pituitary cells. Moreover, it was found that addition of a lpha-subunit to the culture medium enhanced PRL release. The results r aise the possibility that alpha-subunit secreted by PRL cells acts as an autocrine and/or paracrine factor. (C) 1996 Academic Press, Inc.