Histological and steroidogenic changes in dominant ovarian follicles during oestradiol-induced atresia in heifers.
Histological and steroidogenic changes within dominant ovarian follicles (DFs) undergoing atresia following systemic administration of oestradiol benzoate (ODB) were characterized in beef heifers. At 5.6+/-0.1 days after the onset of oestrus, heifers received 1 mg ODB i.m./500 kg body weight (ODB; n=15) or served as controls (n=15). Timing of treatment initiation was designated as hour (h) 0 on day (d) 0, and coincided with the presence of the DF of the first follicular wave (DF1). Within treatments, the DF1 was collected following ovariectomy in four animals at h 12, h 36 or after ultrasonic detection of a new wave (NW) of ovarian follicular development. In heifers of the NW groups (n=7 per treatment), blood samples were collected at intervals of 20 min for 12 h beginning at h-12, 0, 24 and 48 to characterize circulating LH patterns. Administration of ODB suppressed (P<0.01) mean concentrations of LH at h 24 and h 48 by preventing (P<0.05) the increase in LH pulse amplitude observed in controls, but had no effect on FSH. Follicular fluid (FF) concentrations of androgens and oestradiol were reduced at h 36 in the ODB-treated group. The diameter of the DF1 and the number of granulosa cell layers were also reduced in ODB-treated as compared with control heifers. Treatment differences were not observed in the proportion of apoptotic granulosa cells as assessed using the TUNEL assay method, and timing of a new wave of follicular development (d 4.6+/-0.2) was similar (P>0.1) among treatments. A prominent characteristic of oestradiol-induced atresia of the DF1 of the oestrous cycle in heifers was a loss in oestrogenic function associated with reduced LH support. However, the timing of new follicular development may be influenced by a factor(s) other than the status of the DF undergoing oestradiol-induced atresia.
Burke
Christopher R
CR
Department of Animal Sciences, The Ohio State University, Columbus, Ohio 43210, USA.
Cárdenas
Horacio
H
Mussard
Martin L
ML
Day
Michael L
ML
D000818:Animals; D017209:Apoptosis; D002417:Cattle / Q000502:physiology*; D003864:Depression, Chemical; D004958:Estradiol / Q000032:analysis / Q000097:blood / Q000494:pharmacology*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D005496:Follicular Atresia / Q000187:drug effects*; D015571:Follicular Fluid / Q000737:chemistry; D006107:Granulosa Cells / Q000166:cytology; D007986:Luteinizing Hormone / Q000032:analysis*; D008856:Microscopy, Fluorescence; D006080:Ovarian Follicle / Q000033:anatomy & histology* / Q000187:drug effects / Q000378:metabolism*; D010052:Ovariectomy; D011374:Progesterone / Q000097:blood; D011863:Radioimmunoassay / Q000379:methods; D013739:Testosterone / Q000032:analysis
D013739:Testosterone; D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone