Figure 8.

Overexpression of STAT5b mimics and potentiates the effects of PRL on β-cell gene expression. INS-1 832/13 cells were transfected with recombinant adenoviruses expressing a constitutively active, murine STAT5b adenovirus, or green fluorescent protein (GFP; control). After 24 h of transduction, the conditioned media was analyzed (A) for STAT5 protein using a polyclonal antibody to STAT5. The cells were washed with basal media and then incubated for an additional 24 h with PRL (20 nm) or diluent. mRNA levels were measured by quantitative PCR. Values in diluent-treated control cells expressing green fluorescent protein (control) were adjusted so that the mean equaled 1.0; values for STAT5b-expressing and hormone-treated cells were calculated as a function of the mean of control values. B, Means ± sem of all data from two independent experiments, each of which contained four flasks per group. Statistically significant differences between the experimental (hormone treated) and control groups are indicated by asterisks. *, P < 0.05; **, P < 0.01; ***, P < 0.001. Statistical differences between the DEX group and the PRL + DEX group are indicated by the P values above the horizontal connecting lines.