CHANGES IN GLUCOCORTICOID RECEPTOR LEVELS OF BOVINE LYMPHOCYTE AND NEUTROPHIL DURING ESTROUS-CYCLE

Four Bos taurus indicus x Bos tau, us taurus 2 year-old heifers, were studied during the estrous cycle. The relationship between the counts of neutrophils, lymphocytes and the glucocorticoid receptor (GR) sites of these cells were evaluated. Based on the observation of the sponta neous estrous onset, the cycle was divided into P, E, M and D phases. The results showed a significant increase in neutrophil counts (p < 0. 05) during the estrous day (E phase). The GR concentration in the neut rophils increased (p < 0.05) during P and E phases (estrogenic stages) (3924 +/- 1221 versus 2809 +/- 459 sites/cell), while GR sites in the lymphocytes increased (p < 0.05) at the D phase (progesteronic stage) (7491 +/- 515 versus 5429 +/- 1489 sites/cell). The data suggest that the increase in plasmatic cortisol previously linked to ses the P, E, M phases, could be associated with the rise in neutrophils and their GR during the estrogenic phase. A different situation seems to occur w ith lymphocytes. The cortisol decrease known to occur at the progester onic phase, could be linked to an increase in concentration of their G R. These changes suggest a role for steroid hormones as modulators of circulating neutrophil and lymphocyte via their GR.