Angiotensins II and IV stimulate the rat anterior pituitary cell proliferation independently of the AT1 receptor subtype.

OBJECTIVES The purpose of this study was to investigate the effect of angiotensin II (AII) and angiotensin IV (AIV, 3-8 fragment of AII) on the cell proliferation in the anterior pituitary of rat in vivo. MATERIALS AND METHODS The female adult Wistar rats, ovariectomized 10 days before experiment were injected intraperitoneally with saline, AII, AIV and AII or AIV together with losartan--the specific AT1 receptor subtype antagonist. Bromodeoxyuridine (BrDU) incorporation into anterior pituitary cell nuclei was used as the index of cell proliferation. RESULTS We observed the increased BrDU-labeling index (LI) in the anterior pituitary of rat treated with either AII or AIV. The proliferogenic effect of neither AII nor AIV was reversed by AT1 specific antagonist losartan. CONCLUSIONS AII and AIV stimulate the rat anterior pituitary cell proliferation in vivo. This action of both angiotensin peptides is connected with activation of receptor different from AT1 subtype.