Prolactin is an autocrine or paracrine growth factor for human myometrial and leiomyoma cells

To test the hypothesis that prolactin (PRL) acts as a mitogenic growth factor for human leiomyoma and myometrial cells.

To test this hypothesis, we performed three different types of experiments. First, we assessed whether exogenous PRL acted as a mitogen for cultured uterine smooth muscle cells. Second, we examined the role of endogenous PRL by assessing the cell number after exposure of the cultures to a neutralizing antibody to PRL. Finally, we examined both fresh tissues and cultured cells for expression of the PRL receptor messenger ribonucleic acid using the techniques of reverse-transcriptase polymerase chain reaction and Southern blotting.

A significant suppression in cell number was seen after 5 days of culture for leiomyoma cells but not for myometrial cells after treatment with exogenous PRL. Both cell types showed a significant decrease in cell number after treatment with anti-PRL antibody. A 893-bp segment consistent with the cytoplasmic domain of the long form of the PRL receptor was amplified from both fresh and cultured tissues and confirmed by Southern blotting and sequencing.

PRL appears to be an autocrine or paracrine growth factor for both leiomyoma and myometrial cells. However, there are some differences between tissues in their sensitivity to this growth factor.