Temporal gene expression in bovine corpora lutea after treatment with PGF2alpha based on serial biopsies in vivo

Abstract

There is growing evidence to indicate that PGF(2alpha)-induced luteolysis involves altered gene expression in the corpus luteum. Concentrations of mRNA encoding nine different gene products were quantified at three time points from corpora lutea in situ. Serial luteal biopsies (2.1-5.5 mg per biopsy) were collected using an ultrasound-guided transvaginal method and mRNA concentrations were quantified with standard curve quantitative competitive RT-PCR. In the first experiment, three luteal biopsies were collected from three heifers and analysed in multiple assays to evaluate the repeatability of the methods. Concentrations of mRNA for glyceraldehyde 3-phosphate dehydrogenase (GAPDH), PGF(2alpha) receptor (FP receptor) and LH receptor were found to be highly repeatable between assays, between multiple biopsies and between animals (coefficients of variation 1.3-17.3%). In the second experiment, heifers on days 9-11 after ovulation were assigned randomly to receive saline only (n = 6), saline with biopsies taken at t = 0, 0.5 and 4.0 h after injection (n = 6), PGF(2alpha) only (n = 6) or PGF(2alpha) with biopsies taken at t = 0, 0.5 and 4.0 h after treatment (n = 7). Biopsy alone did not change corpus luteum diameter, serum progesterone concentrations or days to next ovulation within the saline- or PGF(2alpha)-treated groups. Concentrations of mRNA for steroidogenic acute regulatory protein, FP receptor, 3beta-hydroxysteroid dehydrogenase, cytosolic phospholipase A(2) and LH receptor were decreased at 4.0 h after PGF(2alpha) injection. In contrast, PGF(2alpha) increased mRNA concentrations for prostaglandin G/H synthase-2, monocyte chemoattractant protein-1 and c-fos but the time course differed for induction of these mRNAs. Concentrations of mRNA for GAPDH did not change after PGF(2alpha) treatment. In conclusion, the techniques allowed analysis of multiple, specific mRNAs in an individual corpus luteum at multiple time points without altering subsequent luteal function. Use of these techniques confirmed that luteolysis involves both up- and downregulation of specific mRNA by PGF(2alpha).