RESUMEN
Although somatotropes of the pituitary gland which secret growth hormone occupy the highest percentage among pituitary hormone cells, the regulatory mechanism of the somatotropes has not been investigated as much as that of the mammotropes. The present study was performed to investigate the direct effects of estrogen on the somatotropes after estrogen treatment in culture of rat pituiary cells. Quantification of bromodeoxyuridine (BrdU)-labeled cells after double immunocytochemistry for BrdU and growth hormone (GH) or prolactin (PRL) demonstrated that estrogen treatment did not bring about the difference in either BrdU labeling index (BLI), apoptosis or cell number of somatotropes. In comparison, estrogen increased the BLI and relative cell number of mammotropes. It was suggested that the changes in the relative cell number of the somatotropes or mammotropes do not attribute to cell death, but to cell proliferation.