[Effect of dopamine and bromocriptine on secretion of growth hormone by pituitary growth hormone secreting tumor in cell culture].

This article reports the effect of dopamine (DA) and its agonist bromocriptine (CB154) on the secretion of growth hormone (GH) by pure GH-secreting pituitary tumor in cell culture as well as a comparison of the effects of these dopaminergic drugs and SMS201-295 (SMS). DA of 10(-8) and 10(-7) mol/L reduced GH secretion to 50.6 and 44.4% of the control, respectively, in 1 out of 6 tumors. CB154 of 10(-7) and 10(-6) mol/L suppressed GH secretion to 59.0 +/- 8.9% of the control in 3 out of 4 tumors. CB154 was at least 10 times less potent than SMS vis a vis GH secretion. CB154 of 10(-6) mol/L inhibited GH secretion to 63.3 +/- 13. 8% (n = 4), but SMS of 10(-7) mol/L induced GH secretion to 45.5 +/- 13.1% (n = 4), the concentration difference between CB154 and SMS was 10 times. CB154 suppressed not only GH secretion, but also GH synthesis in two tumor cell cultures. The major role of SMS in GH secretion was inhibition. The results suggest that DA and CB154 have direct inhibitory effects on GH secretion, at least in some pure pituitary GH secreting tumors. The activities of DA and CB154 are not entirely the same as that of SMS.