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.