Thirteen animals had systemic progesterone concentrations consistent with a functional CL (systemic progesterone concentration > 1 ng/ml) at the time of slaughter. Plasma progesterone concentration (mean ± SEM) was 3.6 ± 1.0 ng/ml (range 1.9-6.9 ng/ml). Five animals had undergone luteolysis at the time of slaughter (systemic progesterone concentration < 1 ng/ml). The mean plasma progesterone concentration for these animals was 0.6 ± 0.13 ng/ml (range 0.2-0.9 ng/ml). antibiotics levaquin
PGFM is an accurate indicator of PGF2a concentrations in plasma, but analysis of single daily blood samples for PGFM concentrations is of limited use because of the pulsatile nature of PGF2a release. However, previous studies using the same assay technique have demonstrated that systemic concentrations of more than 300 pM (105 pg/ ml) are only likely to occur during luteolysis. Therefore PGFM concentrations were used to identify animals that experienced luteolytic concentrations of PGF2a prior to, or at the time of, slaughter.
The 5 animals that had undergone luteolysis all showed PGFM concentrations higher than 105 pg/ml in at least 1 sample collected either 1 or 2 days before or at the time of slaughter. Nine of the twelve animals with a functional CL (progesterone > 1 ng/ml) at the time of slaughter had PGFM concentrations higher than 105 pg/ml on the day of slaughter (range 108-243 pg/ml), but all samples collected from these animals in the days preceding slaughter contained less than 105 pg/ml PGFM (range 45-78 pg/ml). These results, in combination with the progesterone results, indicate that these cows were undergoing luteolysis at the time of the trial as would be expected at this stage of the estrous cycle. During natural luteolysis, progesterone concentrations do not fall to below 1 ng/ml (taken to indicate completion of functional luteolysis) until 36-48 h after the first large pulses of PGF2a are released.
FIG. 1. RT-PCR of MCP-1 (a) and ATPase (b) mRNA expression in CL collected before (lanes 1-3) and after (lanes 4-8) the onset of functional luteolysis. The PCR products were analyzed on a 4% agarose gel stained with ethidium bromide. The sizes (bp) of the amplified products are indicated on the left of the gel. Size markers are shown in lane 9.
FIG. 2. MCP-1 mRNA expression in bovine CL collected from cows before (n = 9, mean ± SEM, hatched bars) and after (n = 5, mean ± SEM, open bars) the onset of functional luteolysis. The figure shows the results from 2 repeated RT-PCR experiments. Expression of mRNA (arbitrary units) was measured by image analysis of agarose gels in which the RT-PCR-amplified cDNA product was visualized after ethidium bromide staining. *p < 0.05 compared to preluteolytic CL.