Antiporcine relaxin (antipRLX540) treatment decreases relaxin plasma concentration and disrupts delivery in late pregnant pigs

摘要

An antibody against pig relaxin (antipRLX540; 1:950 000) was produced in sheep and used to determine the effect on relaxin and progesterone secretion, and on parturition in late pregnant pigs. Large White gilts with normal oestrus cycles were bred on the second observed oestrus and fitted with an indwelling jugular cannula and an intraperitoneal cannula on day 100 of pregnancy. Gilts were infused at 6-h intervals with antipRLX540 (n = 10) or phosphate-buffered saline (PBS) (n = 10) beginning on day103 until parturition. From day 103 to 120, daily blood samples (10 ml) were collected for radioimmunoassay of relaxin, progesterone and prolactin. Bred gilts were randomly assigned to antipRLX540 (n = 11), relaxin (n = 5), and PBS (n = 8) treatments ondays 111, 113 and 115. Blood was collected twice daily from day 108 to 120, and every 20 min on days 111, 113 and 115, beginning 60 min before treatment and continuing for 180 min. Parturition in gilts given antipRLX540 occurred on day 112.7 compared with day 114.0 in relaxin-treated gilts and day 114.3 in PBS-treated controls (P<0.05). Duration of delivery from first to last piglet was delayed in antipRLX540 gilts (240 min) compared with controls ((117 min) P<0.005). The average number of stillbirthswas greater in antipRLX540- than in PBS-treated controls (2.4 vs. 1.0; P<0.05). Relaxin concentration in peripheral plasma was lower in antipRLX540-treated gilts from day 105 to 110, but on day 113 the antipRLX540-treated group had a greater relaxin peakrelease compared with PBS-treated animals (P<0.05). Plasma progesterone concentrations were similar in antipRLX540- and PBS-treated gilts throughout the period of the study. By day 113, progesterone had decreased in antipRLX540-treated gilts compared with relaxin- and PBS-treated gilts. Prolactin levels were similar in antipRLX540- and PBS-treated gilts; from 1 to 3 days post partum the antipRLX540 group had higher prolactin concentrations (P<0.05). AntipRLX540 increased the duration of delivery of piglets and the average number of stillbirths compared with PBS-treated controls.