On the role of 'in vivo' injected progesterone and of the 'in vitro' presence of oxytocin, modulating Ca2+ uptake by the rat uteri from spayed animals and as controllers of the production of arachidonic acid metabolism.

We attempted to explore possible mechanism(s) subserving the influence of oxytocin (O) and of progesterone (P) in the isolated rat uterus studying the action of these hormones on: the synthesis and release of prostaglandins (PGs), the metabolism of labelled arachidonic acid and the uptake of Ca2+ by the tissue from ovariectomized animals. The experiments were done with uterine preparations isolated from spayed rats treated or not with P prior to sacrifice and afterward incubated or not with O 'in vitro'. While uterine strips from untreated spayed rat uterus exhibited a basal release into the incubating medium of approximately the same amounts of PGF2 alpha, and PGE2, the 'in vitro' addition of O (50 mU/ml) increased significantly (p < 0.05) the output of PGF2 alpha without changing the release of PGE2. In tissue from rats injected with P prior to sacrifice the output of PGF2 alpha rose significantly (p < 0.01) as it did after the addition of O to preparations obtained from spayed rats treated with P in comparison to findings in uteri from spayed rats but not in comparison to uteri from spayed rats treated with P alone. Moreover, the 'in vitro' addition of O (50 mU/ml) only increased the formation of PGF2 alpha (p < 0.05) and of 5-HETE (p < 0.05); nevertheless the administration of P to spayed rats diminished significantly (p < 0.05) the formation of 6-keto-PGF1 alpha from uteri, but increased that of PGF2 alpha (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)