Follicle profile and plasma gonadotropin concentration in pubertal female ponies.
Twelve female ponies were examined daily for 30 days and classified as ovulating (OV; N = 6; 197 +/- 6 kg) or prepubertal (PP; N = 6; 196 +/- 9 kg). Follicles were detected by ultrasound and gonadotropins quantified by radioimmunoassay. The mean diameter of the largest follicles was significantly larger in OV (38 +/- 1 mm) than in PP (26 +/- 2 mm) but there was no difference between groups in the size of the second largest follicle. There were more small follicles (<24 mm) in the PP than in the OV group, but PP fillies had a smaller number of follicles >29 mm than the OV fillies. Follicle-stimulating hormone (FSH) levels did not differ between groups but PP fillies had lower luteinizing hormone (LH) peak (8 +/- 1 ng/ml) and basal (4 +/- 0.5 ng/ml) levels, lower peak magnitude (2 +/- 0.2 ng/ml) and period average (5 +/- 0.6 ng/ml) than OV fillies (32 +/- 4.5, 8 +/- 1.2, 17.1 +/- 6, and 15 +/- 2.3 ng/ml, respectively). The PP group, in contrast to the OV group, showed no relationship between FSH surge and follicle wave emergence. We conclude that an LH concentration higher than 8 ng/ml is needed for follicle growth to a preovulatory size. Wave emergence and FSH secretion seem to be independent events, probably due to an inhibitory neural system in these PP animals. PP fillies may provide a physiological model for the study of follicle wave emergence which apparently does not depend on gonadotropin levels.
Nogueira
G P
GP
Departamento de Apoio, Produção e Saúde Animal, Faculdade de Medicina Veterinária, Universidade Estadual Paulista, Araçatuba, SP, Brasil. gpn@fmva.unesp.br
D000818:Animals; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood*; D006736:Horses; D007986:Luteinizing Hormone / Q000097:blood*; D006080:Ovarian Follicle / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D011863:Radioimmunoassay; D012741:Sexual Maturation; D014463:Ultrasonography
D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone