Effects of gonadotropins on testis cell subpopulations of newly hatched chicks treated during embryonic development

•FSH and LH exert differential effects on the chick testis accelerating their growth.•Sertoli cells were the most numerous cell type in testes of FSH-treated chick.•Germ cells were the most numerous cell type in testes of LH-treated chick.•FSH stimulated hypertrophy of Leydig cells but not hyperplasia.•LH stimulated hyperplasia and hypertrophy of Leydig cells. The aim of the present study was to evaluate histological and stereological changes, as well as the variations in the number and size of cells from diverse cell subpopulations in testes of newly hatched chicks treated with follicle stimulating hormone (FSH) and luteinizing hormone (LH) during embryonic development. Stereological results indicated that in FSH-treated chicks total volume of the tubular compartment constitutes most of the testis. In contrast, the total volume of interstitial tissue constitutes most of the testis of LH-treated chicks. Results indicate that the number of germ and Sertoli cells increases as a result of FSH and LH treatment, but in FSH-treated testis, Sertoli cells were the most numerous cell type in seminiferous tubules; whereas germ cells were the most numerous cell type in testis of LH-treated chicks. Results also indicate there was a larger total volume of Leydig cells in the testes of FSH- and LH-treated chicks. The larger volume of Leydig cells in FSH-treated chicks is due to a larger cellular volume of these cells, and not due to the number, which remains constant. In contrast, in testes of LH-treated chicks, there is a larger number and volume of Leydig cells. These results indicate the testes of chick embryos respond to FSH and LH treatment, with there being modifications in the seminiferous tubules and interstitial tissue, but these changes differ markedly, indicating that FSH and LH have differential effects on chick testes.