Immortalized anterior pituitary alpha T3 gonadotropes contain functional luteinizing hormone/human chorionic...

Immortalized alpha T3 gonadotropes contain a major 5.0-kb and minor 3.6-, 2.4- and 1.6-kb luteinizing hormone/human chorionic gonadotropin (LH/hCG) receptor transcripts and an 80-kDa receptor protein which can specifically bind 125I-hCG. The relative abundance of the receptors in alpha T3 cells is, however, lower than in gonadal tissues. Culturing alpha T3 cells with highly purified hCG resulted in a dose- and time-dependent and hormone-specific increase in steady-state levels of LH-alpha subunit mRNA. Culturing alpha T3 cells with hCG also resulted in a concomitant increase in the LH-alpha protein levels. As expected, culturing with GnRH also resulted in an increase of LH-alpha subunit mRNA and protein levels. In summary, we conclude that alpha T3 cells contain LH/hCG receptors which are functionally coupled to the up-regulation of LH-alpha subunit gene expression.