Evidence for a trophic action of the glycoprotein hormone alpha-subunit in rat pituitary.

The effect of the alpha-subunit of luteinizing hormone (LH alpha) on lactotroph growth in 14-day-old rat pituitary was studied in vitro using a reaggregate pituitary cell culture system. LH alpha significantly expanded both the total population of cells expressing prolactin mRNA and the number of [3H]thymidine incorporating prolactin mRNA expressing cells. No such effect could be elicited by LH. Both effects were inhibited by simultaneous addition of an anti-LH alpha antiserum but not by normal rabbit serum. Anti-LH alpha antiserum added alone to the cultures caused a small decrease in the number of prolactin mRNA expressing cells and in [3H]thymidine labelling of the latter. It is concluded that LH alpha may be a trophic factor of lactotrophs not only during fetal development, as suggested by others previously, but also during the rapid expansion of this cell type during postnatal life in the rat.