Resumen

ESPINOZA-VILLAVICENCIO, José Luis et al. OVARIAN FOLLICULAR GROWTH IN DOMESTIC ANIMALS: A REVIEW. INCI [online]. 2007, vol.32, n.2, pp.93-99. ISSN 0378-1844.

Follicular development during a reproductive cycle in the ovaries of most domestic animals follows a pattern of two or three waves or groups. During that process, three different physiological events have been identified: recruitment, selection and dominance of the larger follicles over smaller ones. A group of primordial follicles is recruited in each wave, which then grow. Selection of a dominant follicle occurs at the end of the common growth phase. The dominant follicle grows at a constant rate, and weaker follicles undergo atresia, or they grow temporarily at a reduced rate and later succumb. Follicular deviation is a relatively new concept in understanding dominant follicle selection. Deviation refers to a well-known difference in the growth rate between the two largest follicles present in the ovary in a single pregnancy female. The physiological mechanisms implied in the processes of deviation and selection have not been defined completely, but apparently they are related to the acquisition of luteinizing hormone receptors in the granulose of the dominant follicle, an increase in its estradiol production, and to a reduction in circulating concentrations of the stimulating follicle hormone. The IGF system is also implied by its insulin growth factors (IGF-1 and -2), binding proteins (IGFBP-1, -2, -3, -4, -5 and -6), and specific proteases that degrade the IGFBPs. The endocrine, paracrine and autocrine relationships in follicular growth are described, with emphasis on the mentioned physiological factors involved in the processes of deviation and selection.