RGS3 inhibits GnRH-stimulated LH secretion. Rat anterior pituitary cells were infected or not with adeno-βgal or adeno-RGS3, and 72 h later treated with GnRH to stimulate LH secretion. Upper panel: Adeno-βgal infection was used to determine the fraction of total pituitary cells infected at each dose of adenovirus. Cell viability was measured as trypan blue exclusion. Middle panel: Adeno-βgal infection at various doses was used to control for the effect of RGS3 on GnRH-stimulated LH secretion. No dose of adeno-βgal had an effect on LH release (p < 0.05). Bottom panel: Dose-response relationship between dose of adeno-RGS3 and GnRH-stimulated LH secretion. Adeno-RGS3 doses of 0.2 M.O.I. and higher significantly inhibited LH release (p < 0.05); doses of 2.0 and 5.0 M.O.I, suppressed LH secretion to levels that were not significantly different from their cohorts not treated with GnRH (p < 0.05). Data are mean ± SEM of three independent experiments.