The presence of the pertussis toxin (PTX) insensitive GTP-binding proteins (G-proteins) Gqα and/or G11α has been demonstrated in three different prolactin (PRL) and growth hormone (GH) producing pituitary adenoma cell lines. Immunoblocking of their coupling to hormone receptors indicates that Gq and/or G11 confer throliberin (TRH) responsive phospholipase C (PL-C) activity in these cells. The contention was substantiated by immunoprecipitation analyses snowing that anti Gq/11α-sera coprecipitated PL-C activity. In essence, only Gq/11 (but neither Gi2, Gi3 nor Go) seems to mediate the TRH-sensitive PL-C activity, while Go may be coupled to a basal or constitutive PL-C activity. Immunoblocking studies imply that the Bγ-complex also, to some extent, may stimulate GH3 pituitary cell line PL-C activity. Finally, the steady state levels of Gq/11α mRNA and protein were downregulated upon long term exposure of the GH3 cells to TRH (but not to vasoactive intestinal peptide = VIP).

This content is only available as a PDF.
You do not currently have access to this content.