Seasonal reproduction in the mare: possible role of plasma leptin, body weight and immune status.
ABSTRACT The primary objective of this study was to evaluate the possible role of leptin, body weight and immune status on reproductive activity throughout the transition period from cyclicity to seasonal anestrus, during anestrus and resumption of ovarian activity in Lusitano mares. Mares in good body condition were monthly monitored throughout 2 years (10 mares in each year) for evaluation of their reproductive status by sequential ultrasonography and plasma progesterone determinations. On the second year, all mares were weighed. Progesterone and leptin were assayed by radioimmunoassay (RIA). Parameters of the immune status (phagocytosis and oxidative burst of neutrophils, characterisation of circulating lymphocyte subsets) were also evaluated. Phagocytosis and oxidative burst in blood neutrophils were measured by flow cytometry using commercially available kits. Lymphocyte subsets were assessed by indirect immunofluorescence staining after incubation with monoclonal antibodies specific for CD2, CD19, CD4, CD8 cells markers by flow cytometry. Natural killer cells and B cells were estimated mathematically. No significant difference was found in phagocytosis, oxidative burst and circulating lymphocyte subsets at anestrus and at either phase of the estrous cycle (p>0.05), suggesting that the immune status of the mare was not influenced by the seasonal changes in ovarian activity. This study also suggests that body weight has a direct relationship with plasma leptin levels. Increased concentrations of this hormone in circulation might be associated with the restart or maintenance of ovarian cyclicity in Lusitano mares.
Article: Seasonal variations in serum concentrations of melatonin, testosterone, and progesterone in Arabian horse[show abstract] [hide abstract]
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. Arap atlarında serum melatonin, testosteron ve progesteron seviyelerinin mevsimsel değişimleri Özet: 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. Anahtar sözcükler: Arap atı, fotoperiyod, melatonin, progesteron, testosteron.01/2009; 56:19-24.