GH3 cells expressing constitutively active Gs alpha (Q227L) show enhanced hormone secretion and proliferation

cAMP levels in GH3gsp cells (Q227L mutation of Gs alpha), in comparison with uninfected GH3 and GH3vt (with vector alone) cells, were two to three fold (P < 0.01) higher (basal), and 10-20 fold (P<0.001) higher (in the presence of isobutyl methylxanthine, (IBMX)). Proliferation of GH3gsp cells after 7 days in culture, as determined by cell number and [H-3]thymidine incorporation, were up to 25% (respectively P < 0.001 and P < 0.02) higher. After chronic (4 days) but not acute (15 min) exposure to forskolin (10 mu M) or dibutyryl cAMP (50 mu M) all cell types showed a greater than 200% (P < 0.001) increase in [H-3]thymidine incorporation. Secretion of prolactin and growth hormone by GH3gsp cells were two to four fold (P < 0.001) higher than GH3 and GH3vt cells after 4 h and 10-12 fold (P < 0.001) higher after 8 h. In conclusion GH3 cells possessing Q227L have a higher proliferation rate and secrete higher levels of prolactin and growth hormone which are associated with higher levels of cAMP. (C) 1997 Elsevier Science Ireland Ltd.