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, on the estradiol-induced cell proliferation in the rat anterior lobe and the pars intermedia of the pituitary gland was investigated. The in vivo labelling with bromodeoxyuridine (BrdU) and immunohistochemical staining with anti-BrdU monoclonal antibody was used as an index of pituitary cells proliferation. It was found that enalapril in a dose of 25 mg/kg body weight significantly suppressed BrdU incorporation into anterior 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 index was stated (r = -0,6248; p < 0,05). This finding, taken together with the previous observations, suggests the involvement of the pituitary renin-angiotensin system in estrogen-induced pituitary hyperplasia.