Histological and steroidogenic changes in dominant ovarian follicles during oestradiol-induced atresia in heifers

Abstract

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 6 0.1 days after the onset of oestrus, heifers received 1 mg ODB i.m./500 kg body weight (ODB; n 5 15) or served as controls (n 5 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 5 7 per treatment), blood samples were collected at intervals of 20 min for 12 h beginning at h 2 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 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.Reproduction (2005) 129 611-620

Changes in the glucose-6-phosphate dehydrogenase activity in granulosa cells during follicular atresia in ewes

“…These results agree with previously reported data (Burke et al 2005) and support the morphological classification of follicles.…”

Sphingosine-1-phosphate and ceramide are associated with health and atresia of bovine ovarian antral follicles

“…Therefore, the increase in CER concentrations found in the granulosa cells of antral atretic follicle (>8 mm) in our study, could be associated to the reduced LH stimulus reported in this type of follicle (Aerts and Bols, 2010). Furthermore, reduced LH stimulus in atretic follicle is linked to E2 production decrease and P4 production increase in the follicular fluid (Burke et al, 2005). Our results show that in the atretic follicles, in which P4 concentrations are dominant, the S1P/CER ratio diminishes drastically in the granulosa cells (S1P/CER 45.1 v. 0.5) and in the theca cells (S1P/CER 17 v. 3.1) compared with healthy follicles in which E2 concentrations are dominant.…”

The life and death of the dominant follicle

“…It is well known that estradiol increases proliferation of granulosa cells of numerous species ( Drummond and Findlay, 1999 ; Rosenfeld et al ., 2001 ), enhances cell cycle progression from G1 to S phase ( Quirk et al ., 2006 ), and protects cells against FASLG- and FGF18-induced apoptosis ( Quirk et al ., 2006 ; Portela et al ., 2015 ). It should be noted here that exogenously administered systemic estradiol induces atresia of the dominant follicle ( Burke et al ., 2005 ) by reducing LH pulse amplitude as well as FSH secretion ( Price and Webb, 1988 ).…”