Effects of age and steroid treatment on prostaglandin production by the rat uterus in relation to implantation.

Prostaglandin (PG) production by the uterus of ovariectomized virgin rats, with and without replacement steroid therapy, was compared in animals aged 4-5 and 13-14 months. The synthesizing capacities of the uterus for PGE-2, PGF-2 alpha. 6-keto-PGF-1 alpha and thromboxane (TX) B-2 (expressed as the amounts synthesized per mg protein by the homogenized tissue during a 90-min incubation) were significantly lower in the ageing uteri than in young uteri. The PG and TX synthesizing capacities of the young uteri, but not of the ageing uteri, were stimulated by sequential treatment with oestradiol and progesterone implants. Tissue concentrations in and release from the uteri of PGE-2, but not of PGF-2 alpha, were significantly lower in ageing rats than in younger rats, and occurred irrespective of the hormonal status. Treatment with steroids did not stimulate the tissue concentrations in or release from the uterus of PGE-2 or PGF-2 alpha in young or ageing rats. Since PGs, particularly PGE-2, produced by the rat uterus have been implicated as mediators of the implantation process, reduced production of PGE-2 by the ageing uterus may explain the lower implantation rate and the consequent reduction in fertility of ageing rats.