Leukocyte Chemotaxis Activity by Cotyledons of Dairy Cows With Normal Delivery and Retained Placenta

Abstract

This study aimed to determine the morphology of placentome carunular crypts and neutrophil chemotaxis response by cotyledons of normal and retained placentas of dairy cows, and to determine the effects of 5mg of dexamethasone on placental hormone profiles, placentome morphology and PMN chemotaxis response. Experiment 1: Group 1 comprised normally calving cows with non-retained placentas. Jugular blood samples and placentomes were collected soon after parturition (Group 1), and at 8 hours after parturition (Group 2). Neutrophils were isolated for chemotaxis under agarose, and placentomes were used for morphologic evaluation, and as a source of cotyledon homogenates for chemotaxis assays. Experiment 2: Group 1 comprised saline-treated cows and Group 2 consisted of cows dexamethasone-treated on Day 265 of pregnancy. All animals were ovariectomized on Day 265, catheters were placed into a jugular and uterine vein for blood samples collection, and placentomes were collected through a uterine wall incision. Twenty mg of chlormadinone acetate were given daily to each animal. On Day 270 and at parturition blood samples and placentomes were collected and processed as for Experiment 1. Experiment 3: Group 1 consisted of saline-treated cows and Group 2 comprised cows dexamethasone-treated on Day 255 of pregnancy. On Day 250, on all animals, catheters were placed in a jugular and uterine vein as for Experiment 2. Blood samples and placentomes were collected on Days 250 and 260, at parturition and at 8 hours after parturition in cows that retained the placenta, and processed as for Experiment 1. In all animals of Experiments 2 and 3, blood samples were collected 5 times/day to determine concentrations of cortisol, estrone and progesterone. The results suggest the following conclusions: (a) PMNs from normally calving cows with retained placenta apparently have a defective chemotaxis when compared with that of PMNs from non-retained placenta cows; (b) in normally calving cows, the number of carnucular cells is significantly lower in non-retained placenta cows; (3) the number of carnucular cells decreases towards parturition; (d) homogenates of cotyledons from cows with normal release and retained placentas have chemoattractant activity; (e) dexamethasone did not affect placental hormone profile, number of carnucular cells, nor chemotactic activity of PMNs.