Steroids in the equine oviduct: synthesis, local concentrations and receptor expression.
Steroids play an important role in mammalian reproduction and early pregnancy. Although systemic changes in steroid concentrations have been well documented, it is not clear how these correlate with local steroid concentrations in the genital tract. We hypothesised that, in the horse, the preimplantation embryo may be subjected to high local steroid concentrations for several days. Therefore, we measured progesterone, 17-hydroxyprogesterone, 17ß-oestradiol, testosterone and 17a-testosterone concentrations in equine oviductal tissue by ultra-HPLC coupled with tandem mass spectrometry, and progesterone, 17ß-oestradiol, oestrone and testosterone concentrations in oviduct fluid by radioimmunoassay, with reference to cycle stage and side of ovulation. Progesterone concentrations were high in oviductal tissue and fluid ipsilateral to the ovulation side during dioestrus, whereas other steroid hormone concentrations were not influenced by the side of ovulation. These results suggest that the high ipsilateral progesterone concentration is caused by: (1) contributions from the follicular fluid in the oviduct and diffusion of follicular fluid steroids after ovulation; (2) local transfer of steroids via blood or lymph; (3) local synthesis of progesterone in the oviduct, as evidenced by the expression of steroidogenic enzymes; and (4) a paracrine contribution from follicular cells. These data provide a basis for the study of the importance of endocrine and paracrine signalling during early embryonic development in the horse.
Ghent University, Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Salisburylaan 133, 9820 Merelbeke, Belgium.
Hilde
H
Nelis
Ghent University, Department of Veterinary Public Health and Food Safety, Laboratory of Chemical Analysis, Faculty of Veterinary Medicine, Salisburylaan 133, 9820 Merelbeke, Belgium.
Julie
J
Vanden Bussche
University of Warmia and Mazury, Department of Animal Physiology, Faculty of Biology and Biotechnology, Oczapowskiego St. 1A, 10-719 Olsztyn, Poland.
Bartosz
B
Wojciechowicz
University of Warmia and Mazury, Department of Animal Physiology, Faculty of Biology and Biotechnology, Oczapowskiego St. 1A, 10-719 Olsztyn, Poland.
Anita
A
Franczak
Ghent University, Department of Veterinary Public Health and Food Safety, Laboratory of Chemical Analysis, Faculty of Veterinary Medicine, Salisburylaan 133, 9820 Merelbeke, Belgium.
Lynn
L
Vanhaecke
Ghent University, Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Salisburylaan 133, 9820 Merelbeke, Belgium.
Bart
B
Leemans
Ghent University, Department of Morphology, Faculty of Veterinary Medicine, Salisburylaan 133, 9820 Merelbeke, Belgium.
Pieter
P
Cornillie
Ghent University, Department of Nutrition, Genetics and Ethology, Faculty of Veterinary Medicine, Heidestraat 19 , 9820 Merelbeke, Belgium.
Luc
L
Peelman
Ghent University, Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Salisburylaan 133, 9820 Merelbeke, Belgium.
Ann
A
Van Soom
Ghent University, Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Salisburylaan 133, 9820 Merelbeke, Belgium.|Corresponding author. Email: katrien.smits@ugent.be.
Katrien
K
Smits
3ß-hydroxysteroid dehydrogenase; aromatase; cytochrome P450scc; follicular fluid; mare; oviductal fluid; progesterone receptor; serum; steroidogenesis; steroidogenic acute regulatory protein