FIG. 3.

TSHR/IGF-1R cooperativity does not occur via enhancement of the cAMP/PKA pathway. (A) Cells were stimulated with the indicated doses of TSH alone or in combination with 100 ng/mL of IGF-1 in the presence of 1 mM of IBMX for 2 h and cAMP measured by ELISA. The EC₅₀ for cAMP accumulation mediated by TSH in these cells was 79 nM (approx. 1.5 mIU/mL). Data are expressed as mean ± SEM, n = 4. (B) and (C) Cells were treated for 5 or 30 min with the indicated doses of TSH, then washed and lysed for immunoblotting of vasodilator-stimulated phosphoprotein (VASP, a PKA target) and cAMP response element-binding protein (CREB, a PKA-activated transcription factor). Data are expressed as mean ± SEM, n = 4.