Mean log normal concentrations of PGFM in the plasma of OT- and saline-injected cows are shown in Figure 4. After injection of OT, the concentration of plasma PGFM increased linearly over the 90-min experimental period (r = 0.849, p < 0.0001), whereas after saline injection, mean plasma PGFM did not increase (r = 0.154, p = 0.5). In one of the saline-injected controls (gestational age 230 days), plasma PGFM increased somewhat but much less than after OT injection. We attribute the rise in this control cow to stress during the injection and blood-sampling procedures. The individuals conducting the experiments had noted that this particular cow was exceptionally wild and uncooperative during the blood-sampling period. ampicillin antibiotic
Expression of COX-2 mRNA in OT- and Saline-Injected Cows
RPA was performed twice using 20 ^g total RNA from endometrium from each cow. One of the gels is shown in Figure 5. The results were quantified as described above, and the mean relative intensities are shown in Figure 6. The protected fragment for COX-2 mRNA was present in RNA of all three OT-injected cows, whereas only one of the saline-treated cows showed a signal for COX-2 mRNA, which was much weaker than in the OT-treated cows. This cow was the same cow in which plasma PGFM levels were somewhat increased.
FIG. 4. Plasma concentrations of PGFM in midpregnant cows injected with 200 IU OT (squares) or saline (circles). Values are log normal means ± SE. A single asterisk indicates significant difference from basal levels, and two asterisks indicate significant difference between OT- and saline-injected cows (two-way ANOVA followed by least significant difference test, p < 0.05). PGFM concentrations increased linearly during the 90-min collection period in the OT-injected cows (r = 0.854, p < 0.005); no significant change occurred in saline-injected cows (r = 0.150, p < 0.5).
FIG. 5. RPA for COX-2 mRNA and GAPDH mRNA using total RNA from in-tercaruncular endometrium of six pregnant cows (230-270 days gestational age) paired according to gestational age; one in each pair was treated with OT (200 IU) and the other with saline i.v., and cows were exsanguinated 2 h after each injection. Lanes 1-3 are from OT-treated cows, lanes 4-6 from saline-treated cows. All OT-injected cows showed signals for the protected fragment of COX-2 mRNA; only one of the saline-injected cows showed a weak signal for COX-2 mRNA.
FIG. 6. Relative intensity of COX-2 mRNA in percentage of corresponding GAPDH mRNA in ribonuclease protection shown in Figure 5; each sample was collected 2 h after the injection. Values are means from two separate gels; mean ± SE.