Patrícia dos Santos Carneiro; Tais Harumi de Castro Sasahara; Hianka Jasmyne Costa de Carvalho; Maria Angélica Miglino & Silvio Pires Gomes

Nucleolus Organizer Regions (NORs) are defined as nucleolar components containing argyrophilic proteins selectively stained by silver methods (AgNORs). Several investigations have shown the AgNOR quantity and area represent a valuable parameter of cell kinetics, since they reflect the level of activity and cellular proliferation. This article addresses an evaluation of the functional activity and relation between days of pregnancy and proliferative capacity of trophoblastic mononucleate and binucleate cells from bovine placentomes. Both the number and size of AgNORs were determined in different phases of gestation by silver nitrate staining in conventional histological slides. The results showed a significant increase (from 1 to 12 AgNORs) in the number of AgNORS per trophoblastic mononucleate cell in the 3rd trimester, with predominance of 4-6 AgNORs/cell. In the 1st and 2nd trimesters, the number ranged between 1 and 9 AgNORs/cell, with predominance of 1-3 AgNORs. No significant differences were observed between the 2nd and 3rd trimesters, but in the first, in binucleate cells (19-27 and 10-18 AgNORs/cell, respectively) - this number was higher than the one registered in trophoblastic mononucleate cells in the same period. Thus, AgNORs can be used as markers of the proliferative placental cell cycle and established a relation between number of AgNORs and days of gestation. This relation can be used for diagnoses and prognoses of several placental pathologies, including pregnancy losses from manipulated embryos.

KEY WORDS: Nucleolar organizer regions; Placenta; Cellular structures; Pregnancy.

CARNEIRO, P. DOS S.; SASAHARA, T. H .C.; CARVALHO, H. J. C.; MIGLINO, M. A. & GOMES, S. P. Determination of the relationship among cell proliferation, metabolic activity and stage of pregnancy by AgNORs as markers in bovine placenta. Int. J. Morphol., 39(5):1358-1364, 2021.