Seasonal variations in serum concentrations of melatonin, testosterone, and progesterone in Arabian horse

Abstract

The objective of this study was to characterize seasonal variations in serum concentrations of melatonin, testosterone, and progesterone in Arabian horses under natural photoperiodic conditions. Peripheral blood samples were collected during breeding and non-breeding seasons from mares and stallions. Serum concentrations of melatonin, testosterone, and progesterone were determined by radioimmunoassay. Serum concentrations of melatonin were greater in the non-breeding season (42.41±1.59 and 37.68±1.55 pg/ml) when compared to breeding season (23.52±1.24 and 17.22±2.10 pg/ml) in both mares and stallions, respectively. Melatonin concentrations were low but not different between the luteal and follicular phases during breeding season in cyclic mares. Mares had greater concentrations of melatonin than stallions in both breeding and non-breeding season. Mean concentrations of testosterone were greater during breeding season (6.58±0.50 ng/ml) than non-breeding season (3.64±0.48 ng/ml) in stallions. There was a negative correlation (r=-0.658, p<0.01) with melatonin and testosterone levels in both season in stallions. A negative correlation (r=-0.829, p<0.05) in luteal phase and a positive correlation (r=0.847, p<0.05) in non-breeding season were found between melatonin and progesterone concentrations in mares. We conclude that changes in day length act as a regulator and photoperiod can be used to modify the seasonal reproduction in Arabian horse

Keywords

• Arabian horse
• melatonin
• photoperiod
• progesterone
• testosterone

Arap atlarında serum melatonin, testosteron ve progesteron seviyelerinin mevsimsel değişimleri

Abstract

Bu çalışmanın amacı, doğal fotoperiyodik koşullarda Arap atlarının serum melatonin, testosteron ve progesteron seviyelerinin mevsimsel değişimlerini belirlemektir. Kısrak ve aygırlardan üreme döneminde ve üremenin olmadığı dönemde toplanan kan örneklerinden, radioimmunoassay yöntemi ile serum melatonin, testosteron ve progesteron seviyeleri belirlenmiştir. Sırasıyla hem kısrak hem de aygırlarda melatonin seviyeleri üremenin olmadığı dönemde (42.41±1.59 ve 37.68±1.55 pg/ml) üreme dönemine göre (23.52±1.24 ve 17.22±2.10 pg/ml) daha yüksek bulunmuştur. Üreme döneminde östrus siklusu gösteren kısraklarda melatonin seviyelerinin düşük fakat luteal ve foliküler dönemler arasında fark yoktu. Kısraklar hem üreme döneminde hem de üremenin olmadığı dönemde aygırlara göre daha yüksek melatonin seviyelerine sahipti. Aygırlarda üreme dönemindeki (6.58±0.50 ng/ml) testosteron seviyeleri üremenin olmadığı dönemden (3.64±0.48 ng/ml) daha yüksekti. Aygırlarda her iki dönemde melatonin ile testosteron seviyeleri arasında negatif bir ilişki vardı (r=-0.658, p<0.01). Kısrakların melatonin ve progesteron seviyeleri arasında ise luteal dönemde negatif (r=-0.829, p<0.05), üremenin olmadığı dönemde de pozitif bir ilişki (r=0.847, p<0.05) bulundu Bu çalışma ile Arap atlarında, gün uzunluğundaki değişikliklerin mevsimsel üremede bir düzenleyici olarak görev aldığı ve fotoperiyodun bu düzenlemede değiştirici etkisi olduğu bulundu

Keywords

• Arap atı
• fotoperiyod
• melatonin
• progesteron
• testosteron

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