THE EFFECT OF ANGIOTENSIN-CONVERTING ENZYME-INHIBITION ON ESTROGEN-INDUCED CELL-PROLIFERATION IN THE RAT PITUITARY-GLAND

The effect of an angiotensin-converting enzyme inhibitor, enalapril, o n the estradiol-induced cell proliferation in the rat anterior lobe an d the pars intermedia of the pituitary gland was investigated. The in vivo labelling with bromodeoxyuridine (BrdU) and immunohistochemical s taining with anti-BrdU monoclonal antibody was used as an index of pit uitary cells proliferation. It was found that enalapril in a dose of 2 5 mg/kg body weight significantly suppressed BrdU incorporation into a nterior lobe cell nuclei. On the other hand, enalapril did not affect cell proliferation within the pituitary pars intermedia. The negative correlation between tested doses of the drug and the BrdU labelling in dex was stated (r = -0,6248; p < 0,05). This finding, taken together w ith the previous observations, suggests the involvement of the pituita ry renin-angiotensin system in estrogen-induced pituitary hyperplasia.