R. S. Ramos

Manipulation of the periovulatory sex steroidal milieu affects endometrial but not luteal gene expression in early diestrus Nelore cows

In beef cattle, the ability to conceive has been associated positively with size of the preovulatory follicle (POF). Proestrus estradiol and subsequent progesterone concentrations can regulate the endometrium to affect receptivity and fertility. The aim of the present study was to verify the effect of the size of the POF on luteal and endometrial gene expression during subsequent early diestrus in beef cattle. Eighty-three multiparous, nonlactating, presynchronized Nelore cows received a progesterone-releasing device and estradiol benzoate on Day-10 (D-10). Animals received cloprostenol (large follicle-large CL group; LF-LCL; N = 42) or not (small follicle-small CL group; SF-SCL; N = 41) on D-10. Progesterone devices were withdrawn and cloprostenol administered 42 to 60 hours (LF-LCL) or 30 to 36 hours (SF-SCL) before GnRH treatment (D0). Tissues were collected at slaughter on D7. The LF-LCL group had larger (P < 0.0001) POF (13.24 ± 0.33 mm vs. 10.76 ± 0.29 mm), greater (P < 0.0007) estradiol concentrations on D0 (2.94 ± 0.28 pg/mL vs. 1.27 ± 0.20 pg/mL), and greater (P < 0.01) progesterone concentrations on D7 (3.71 ± 0.25 ng/mL vs. 2.62 ± 0.26 ng/mL) compared with the SF-SCL group. Luteal gene expression of vascular endothelial growth factor A, kinase insert domain receptor, fms-related tyrosine kinase 1, steroidogenic acute regulatory protein, cytochrome P450, family 11, subfamily A, polypeptide 1, and hydroxy-delta-5-steroid dehydrogenase, 3 beta- and steroid delta-isomerase 7 was similar between groups. Endometrial gene expression of oxytocin receptor and peptidase inhibitor 3, skin-derived was reduced, and estrogen receptor alpha 2, aldo-keto reductase family 1, member C4, and lipoprotein lipase expression was increased in LF-LCL versus SF-SCL. Results support the hypothesis that the size of the POF alters the periovulatory endocrine milieu (i.e., proestrus estradiol and diestrus progesterone concentrations) and acts on the uterus to alter endometrial gene expression. It is proposed that the uterine environment and receptivity might also be modulated. Additionally, it is suggested that increased progesterone secretion of cows ovulating larger follicles is likely due to increased CL size rather than increased luteal expression of steroidogenic genes.

Regulation of the polyamine metabolic pathway in the endometrium of cows during early diestrus

The timing and magnitude of exposure to preovulatory estradiol followed by post‐ovulatory progesterone (periovulatory endocrine milieu) in cattle modulate endometrial gene expression, histotroph composition, and conceptus development, but the mechanisms underlying this regulation remain unknown. Using an experimental model based on the modulation of follicle growth, this work aimed to evaluate if the polyamine metabolic pathway is regulated by the periovulatory endocrine milieu. Nelore cows were manipulated to ovulate small (n = 15) or large (n = 15) follicles, then the profiles of polyamines and their synthetic enzymes were compared between groups. Transcripts for the enzymes of this pathway, ornithine decarboxylase 1 (ODC1; the rate‐limiting enzyme in polyamine biosynthesis) protein quantification, adenosylmethionine decarboxylase 1 (AMD1) protein immunolocalization, and concentrations of the different polyamines (putrescine, spermidine, and spermine) were respectively quantified by quantitative reverse‐transcriptase PCR, immunoblotting, immunohistochemistry, and gas chromatography‐mass spectrometry in both the endometrium and uterine flushing. No differences in gene and protein expression or concentration of polyamines were observed between groups. There were significant correlations between the relative abundance of ODC1 and spermidine/spermine N1‐acetyltransferase 1 (SAT1) transcripts as well as between antizyme inhibitor 1 (AZIN1) and adenosylmethionine decarboxylase 1 (AMD1) transcripts. In conclusion, our results show that the polyamine metabolic pathway is present and functional, but not regulated by the periovulatory endocrine milieu in the bovine endometrium. Mol. Reprod. Dev. 81: 584–594, 2014.