Pituitary blood was collected from the intercavernal sinus in five mares before and during parturition, and in nine mares immediately after parturition to investigate oxytocin patterns during parturition and early lactation, and to determine the relationship between oxytocin, prostaglandin and arginine vasopressin during parturition. In four mares in which sample collection began at least 6 h before rupture of the chorioallantois, a significant increase (P < 0.05) in PGF 2α concentration was detected before a significant increase in oxytocin concentration. Cross-correlation analysis of log-transformed oxytocin and PGF 2α concentrations revealed a significant correlation (P < 0.05) at a 6 min lag period, indicating that in the 2 h before delivery of the foal, an increase in prostaglandin was followed 6 min later by an increase in oxytocin. A significant effect of suckling on oxytocin release by the mare was detected in only two of nine mares, when oxytocin concentrations were evaluated 0-3 min after suckling. When foals were prevented from sucking for 1 h, by being either muzzled (n = 2) or separated from the mare (n = 2), there was no significant association between resumption of suckling and oxytocin release by the mare. The results of these studies show that: (i) oxytocin secretion from the maternal posterior pituitary gland begins before, or in association with, the onset of the second stage of labour, and that prostaglandin increases in the peripheral circulation before oxytocin release; and (ii) suckling is not significantly related to oxytocin release in mares.

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A rapid, sensitive enzymeimmunoassay for the measurement of LH concentrations in serum and peritoneal fluid samples of healthy women and women with endometriosis is reported. The ligand (LH) was captured by a readily available, widely used and well-characterized monoclonal antibody (mAb, 518B7) generated against the beta subunit of bovine LH. This mAb, although specific for LH, shows very little species specificity and detects LH by radioimmunoassay in humans. A polyclonal antiserum raised in rabbits against hCG was conjugated to horseradish peroxidase and was used as the second antibody signal. This anti-hCG antiserum crossreacts with LH. The enzymeimmunoassay uses the standard human LH (hLH) preparations (NIADDK-hLH-I-3, AFP-827OB) and results are based on the relative concentrations of LH in serum and peritoneal fluid. Total assay time was < 3 h. The range of the standard curve was 0.002-0.500 ng LH per well and the lowest concentration of hLH that could be distinguished from zero concentration was 0.15 +/- 0.02 ng ml(-1) serum and 0.058 +/- 0.021 ng ml(-1) peritoneal fluid. Clinical diagnostic parameters for the LH enzymeimmunoassay showed a sensitivity of 85.71%, specificity 92.50%, efficiency 88.54%, positive predictive value 94.11% and negative predictive value 82.22%. The study was retrospective. Serum LH concentrations of women with endometriosis were 13.67 +/- 7.21 ng ml(-1), whereas serum LH concentrations of women in the control group were 4.52 +/- 2.03 ng ml(-1). One-way ANOVA showed significant differences (P < 0.001) between women with endometriosis and control groups. Women in the control group had peritoneal fluid LH values of 5.65 +/- 2.43 ng ml(-1), whereas peritoneal fluid LH values of 64.06 +/- 16.44 ng ml(-1) were obtained in women with endometriosis (P < 0.001). A cycle-dependent pattern of serum and peritoneal fluid LH concentration was observed in women in the control group, which was not observed in the peritoneal fluid of the group with endometriosis. The application of this assay to serum or peritoneal fluid samples provides the attractive possibility that it could be included in the panel of markers used for diagnosis of endometriosis.