THE ROLE OF PROSTAGLANDINS IN THE MATERNAL RECOGNITION OF PREGNANCY IN MARES
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abstract
Prostaglandin F (PGF) was quantified in intra-uterine luminal flushings, endometrium and in vitro incubations of endometrium alone and endometrium in the presence of conceptus membranes. There were significant day by status interactions in all cases, indicating that the patterns of PGF synthesis and/or secretion were affected differently according to the presence or absence of an embryo. Endometrial PGF content and in vitro production capability both reached peaks on or about day 14 post ovulation in cycling mares then declined following luteolysis. Likewise, uterine luminal PGF peaked abruptly on day 14, remained elevated, then declined to day 20. In contrast, endometrial content of PGF remained lower in pregnant mares until an elevation on day 20, while the in vitro production capability of endometria from pregnant mares continued to increase post day 14. Co-incubation of endometrial tissue and conceptus membranes in vitro, however, reduced PGF production suggesting that embryonic factors may be capable of blocking endometrial PGF synthesis or secretion. PGFM measurements suggested that reduced PGF in uterine luminal flushings or in in vitro incubations was not reflected by a higher rate of metabolism. Corpora luteal PGF receptors retained the ability to bind PGF during early pregnancy. These data suggest that luteal maintenance in pregnant mares may involve inhibition of PGF synthesis and/or release and therefore should be considered luteostasis. 1984.
