RESUMEN
<p><b>AIM</b>To assess whether exogenous estradiol has any effect on migration of primordial germ cells (PGCs) in the chick.</p><p><b>METHODS</b>Fertilized eggs were treated with 17beta-estradiol (E(2)) (80 microg/egg) at stage X (day 0 of incubation), stages 8-10 (incubation 30 h) and 13-15 (incubation 55 h). Controls received vehicle (emulsion) only. Changes in PGC number were measured on different days according to developmental stages.</p><p><b>RESULTS</b>In male right gonads, but not in female left gonads, at stages 28-30 (incubation 132 h) significant decreases in the mean number of PGCs aggregating were observed compared with the controls (P < 0.05) while the total PGC number in the right and left gonads at each stage did not change (P > 0.05).</p><p><b>CONCLUSION</b>The present study provides evidence that E(2) has significant effects on the localization of PGCs in male right, but not female left, gonads of chicken embryos at stages 28-30, compared with controls.</p>