Alterations in plasma and tissue prostaglandin levels in rabbits during luteal regression

To determine if ovarian as well as uterine prostaglandin production was associated with luteal regression, tissue and plasma concentrations of prostaglandin F (PGF), prostaglandin E (PGE), 6-keto-PGF1 alpha (6-keto-PGF), and thromboxane B2 (TxB) were measured by radioimmunoassay in uterus, corpora lutea, nonluteal tissue, uterine venous plasma and ovarian venous plasma on Days 8, 12 and 15 of pseudopregnancy in the rabbit. Total prostaglandin levels (PGF + PGE + 6-keto-PGF + TxB) were 4-fold greater in the uterus compared to nonluteal tissue and 8-fold greater than in corpora lutea. Both PGF and PGE levels were increased in uterine tissue on Day 15 compared to Days 8 or 12 (P less than 0.01). The ratio of PGF:PGE was also elevated on Day 15 compared to Days 8 or 12 (P less than 0.05) which suggests that the luteolytic effect of PGF predominates over the possible luteotropic effect of PGE. There were no significant changes in the concentration of TxB or 6-keto-PGF or the ratio of TxB:6-keto-PGF in uterine tissue on any day studied. In nonluteal tissue, PGE was the only PG to vary significantly; PGE levels were elevated (P less than 0.05) on Day 8 of pseudopregnancy compared to Days 12 or 15. Although corpora lutea contain significant quantities of PGF, PGE, TxB and 6-keto-PGF, no alterations in the levels of any of these substances were observed between Days 8, 12 or 15 of pseudopregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)