Follicular and uterine prostaglandin levels in relation to uterine contraction and the first ovulation of a sequence in the hen

Changes in the concentration of progesterone, estrone, estradiol, prostaglandins (PG) E3, 6-keto F10, F20 and 13,14-dihydro-15-keto F20 (PGFM) were measured in peripheral plasma, and in venous effluent from the shell gland and the largest (F1) and the second largest (F2) preovu-latory follicles. Tissue concentrations in the F1, F2 and the most recently ruptured follicle and the shell gland also were determined. Changes in these criteria were compared to changes in uterine con-traction before the first ovulation of a sequence. Significant increases of PGF20 and PGFM in the peripheral plasma were observed when the freqqency of uterine contraction reached a maximum, about 1 h before ovulation. Relative to peripheral plasma, the concentrations in F1 plasma of progesterone, PGF20 and PGFM were increased 20-fold, 150-fold and 15-fold, respectively, at the time of the maximum frequency of uterine contraction. The highest tissue concentrations of PGs were also observed in the F follicle. These results suggest that the largest preovulatory follicle is the major source of PG synthesis and release. These PG5 may stimulate uterine contraction and may also play a role in follicular rupture and release of the ovum