Figure 1.

Δ1–9-G129R-hPrl inhibits exogenous prolactin effects but does not reduce cell numbers in standard growth conditions. (a) Western analysis of T47D cell lysates confirms prolactin (500 ng/ml for 30 min) induced phosphorylation of STAT 5A/B, which is abrogated in a dose-dependent manner by coincubation with Δ1–9-G129R-hPrl (Δ1–9). (b) Prolactin-induced increase in cell number of T47D cells in monolayer culture for 3 days was abrogated by coincubation with Δ1–9. (c) 1,000 ng/ml Δ1–9 (broken lines) had no effect on cell number in control medium (solid lines) of MCF-7 cells (upper two curves) or T47D cells (lower two curves) in a monolayer culture in the absence of exogenous prolactin. *P < 0.05 by Student t test compared with 100 ng/ml prolactin in the absence of Δ1–9. Error bars, standard error of the mean of triplicate observations. All data representative of at least three experiments.