Placental separation in cattle: Arachidonic acid metabolites, steroids and leukocyte function
Hoedemaker, Martina
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Permalink
https://hdl.handle.net/2142/18961
Description
Title
Placental separation in cattle: Arachidonic acid metabolites, steroids and leukocyte function
Author(s)
Hoedemaker, Martina
Issue Date
1990
Doctoral Committee Chair(s)
Wagner, William C.
Department of Study
Veterinary Biosciences
Discipline
Veterinary Medical Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Animal Pathology
Biology, Veterinary Science
Language
eng
Abstract
In the following investigation, in vivo and in vitro arachidonic acid (AA) and steroid metabolism as well as function of circulating polymorphonuclear neutrophil leukocytes (PMN) during the last month of pregnancy in cows, and possible interrelationships between those three parameters, were studied. Concentrations of 6-keto-prostaglandin F$\sb{1\alpha}$ (6-keto-PGF$\sb{1\alpha}$), prostaglandin F$\sb{2\alpha}$, (PGF$\sb{2\alpha}$) and prostaglandin E$\sb2$ (PGE$\sb2$) in carotid artery blood increased throughout the last month of pregnancy. Concentrations of 6-keto-PGF$\sb{1\alpha}$ and PGE$\sb2$ were higher in uterine vein than in carotid artery blood, a fact which was also observed as a trend for PGF$\sb{2\alpha}$, thromboxane B$\sb2$ and 15-hydroxyeicosatetraenoic acid (15-HETE). Metabolism of AA by fetal placental tissue in vitro was markedly increased as pregnancy progressed. The major metabolites synthesized were: 13,14-dihydro-15-keto-PGE$\sb2$, PGE$\sb2$, 12-hydroxy-heptadecatrienoic acid and 15-HETE. Fetal placental tissue in vitro also produced estrogens in increasing amounts throughout the experimental period. The application of 5 mg dexamethasone to the dam on Day 255 of gestation did not affect placental estrogen synthesis in vitro. In contrast, cortisol applied in vitro stimulated estrogen synthesis in a dose-dependent manner, probably by stimulating enzymes involved in the $\Delta$5 steroidogenic pathway which turned out to be the major placental estrogenic pathway in cows. Iodination of proteins and cytochrome C reduction by PMN, both measures of the oxygen-dependent antimicrobial system, were decreased at parturition, whereas ingestion capacity was stimulated at parturition. Fetal placental tissue and uterine wall tissue extracts attracted PMN, whereas skeletal muscle extracts were without effect. Five eicosanoids (PGF$\sb{2\alpha}$, leukotriene B$\sb4$, 5- and 15-HETE, and lipoxin B$\sb4$), and estrogens were chemoattractant. Prostacyclin inhibited iodination of proteins, whereas PGF$\sb{2\alpha}$ stimulated ingestion capacity of PMN. Conditioned media from cultured fetal placental tissue attracted PMN, stimulated chemotaxis, and inhibited iodination of proteins, cytochrome C reduction and antibody-dependent cell-mediated cytotoxicity. It is concluded that substances produced within the uterine compartment (prostacyclin, PGF$\sb{2\alpha}$) and by the placenta (15-HETE, estrogens) might be associated with the chemoattractant properties of fetal placental tissue and uterine tissues, and the changes in PMN function observed at the end of pregnancy. The latter might render the animal more susceptible to bacterial infections in the periparturient period.
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