A study of prostaglandin F2alpha as the luteolysin in swine: II Characterization and comparison of prostaglandin F, estrogens and progestin concentrations in utero-ovarian vein plasma of nonpregnant and pregnant gilts.

Polyvinyl catheters were inserted into the right and left utero-ovarian veins (UOV) and saphenous vein (SV) and artery (SA) of six non-pregnant (O) and five pregnant (P) gilts on day 11 after onset estrus. Beginning on day 12, UOV blood samples were collected at 15-min intervals from 0800 to 1100 hr and 2000 to 2300 hr, and single samples were taken at 1200 and 2400 hrs. Peripheral blood (SA or SV) was sampled at 0800, 1200, 2000 and 2400 hr until gilts returned to estrus (X = 20.6 days) or day 24 of pregnancy. UOV plasma PGF concentrations (ng/ml; n = 1929) were measured by RIA. Status (P vs O) by day interactions were detected (P less than .01) but variances among treatments were heterogenous (P less than .01). Curvilinear day trends were detected for PGF in 0 gilts (P less than .01) but not P gilts. PGF peaks, defined as concentrations greater than two SD above the mean concentration for each gilt, occurred with greater frequency (chi2 = 16.4; P less than .01) in O than P gilts; and mean peak levels (X +/- SE) were 5.04 +/- .27 and 3.84 +/- .13 ng/ml, respectively. Progesterone concentrations were maintained in pregnant pigs and were indicative of luteal maintenance. Systematic differences in day trends of utero-ovarian venous plasma estradiol were detected between O and P pigs. These differences may be of paramount physiological importance and are discussed.