Effects of age,season, and fertility status on plasma and intratesticular immunoreactive (IR) inhibin concentrations in stallions |
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| Institution: | 1. Eutheria Foundation, Cross Plains, Wisconsin, 53528, USA;2. Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, 53706, USA;1. Eutheria Foundation, Cross Plains, WI, 53528, USA;2. Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI, 53706, USA;3. Department of Animal and Dairy Sciences. University of Wisconsin-Madison, Madison, WI, 53706, USA;4. Division of Animal and Nutritional Sciences, West Virginia University, Morgantown, WV, 26506, USA;1. Department of Large Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, USA;2. Noble Equine Veterinary Service, Purcell, Oklahoma, USA;3. Katy, Texas, USA;4. Houston, Texas, USA;5. Department of Animal and Dairy Science, Mississippi State University, Starkville, Mississippi, USA;1. Faculty of Veterinary Medicine, Department of Animal Medicine and Surgery, University of Cordoba, Cordoba, Spain;2. Centro Militar de Cría Caballar de Ecija, Cría Caballar de las F.A.S., Ecija, Seville, Spain;1. Department of Comparative Biomedical Sciences, The Royal Veterinary College, Hawkshead Lane, Hatfield, Hertfordshire, AL9 7TA, United Kingdom;2. Rossdales Equine Practice, Beaufort Cottage Stables, High Street, Newmarket, Suffolk CB8 8JS, United Kingdom;3. Equine Reproductive Services (UK) Ltd., 33 Westgate, Old Malton, Malton, North Yorkshire, YO17 7HE, United Kingdom;4. Newmarket Equine Hospital, Cambridge Road, Newmarket, Suffolk, CB8 0FG, United Kingdom;5. Department of Production and Population Health, The Royal Veterinary College, Hawkshead Lane, Hatfield, Hertfordshire, AL9 7TA, United Kingdom;1. Laboratory of Semen Biotechnology and Andrology, Department of Animal Reproduction, School of Veterinary Medicine and Animal Science, University of São Paulo (USP), Pirassununga, São Paulo, Brazil;2. Laboratory of Theriogenology Dr. O. J. Ginther, Department of Veterinary Medicine, School of Animal Sciences and Food Engineering, University of São Paulo, Pirassununga, São Paulo, Brazil |
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| Abstract: | The nature of the relationship between inhibin and reproductive function in the stallion is yet to be elucidated. Blood and testes from 51 light horse stallions ranging in age from 2 mo to 25 years were collected during the breeding and nonbreeding seasons to study the effects of testicular maturation, aging, season, and fertility status on peripheral and intratesticular concentrations of Ir inhibin and other reproductive hormones. Of the 51 stallions, 12 age-matched stallions (6 fertile, 3 subfertile, and 3 infertile) were used in the fertility study. Blood samples were taken before castration and plasma stored at ?20°C for analysis of Ir inhibin, luteinizing hormone (LH), follicle stimulating hormone (FSH), testosterone (T), estradiol (E2), and estrogen conjugates (EC) by radioimmunoassay (RIA). Testes were homogenized and testicular extracts prepared and frozen at ?70°C for analysis of Ir inhibin, T, E2, and EC by RIA. Plasma concentrations of Ir inhibin, LH, FSH, T, E2, and EC and intratesticular concentrations of Ir inhibin, T, E2, and EC increased with age (P < 0.01). The most dramatic effect appeared to be during testicular maturation. An aging effect was not observed in adult stallions. A seasonal effect was not detected for any of the plasma hormones, whereas for the intratesticular hormones the only change noted was an increase in T in the nonbreeding season (P < 0.05). Plasma Ir inhibin, E2, and EC were lower (P < 0.01) and gonadotropins higher (P < 0.05) in infertile stallions. Plasma T levels did not change. Intratesticular Ir inhibin concentrations tended to be lower (P < 0.1) in subfertile stallions and significantly lower (P < 0.01) in infertile stallions, whereas intratesticular steroid levels were not different among the three groups. In conclusion, plasma and intratesticular Ir inhibin concentrations seem to be affected by testicular maturation and fertility status. |
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