HISTOCHEMISTRY AS SUPPORTING TOOL IN GRASSLAND ECOSYSTEM MANAGEMENT: APELIN SYSTEM DETECTION IN EWE REPRODUCTIVE APPARATUS

Adipokines are molecules involved in energy metabolism and represent important links between nutritional status, neuro-endocrine axis and healthy pregnancy (1). We analysed the presence of apelin (APLN) and its receptor (APLNR) in the reproductive apparatus of the sheep, into a research project aimed to achieve a sustainable grassland productive ecosystem management. 15 adult female ewes (Comisana x Appenninica) in dry stage were fed with fresh hay from June to the pasture maximum flowering (MxF). From this period to maximum dryness, the control group (Cnt) was fed with fresh hay while, the experimental group (Exp) was also supplemented with 600g/day/head of barely and corn (1:1). Ovary, ampulla and uterus samples were collected at each time and processed to perform RT-PCR, morphological and immunohistochemical analysis. Samples for molecular biology were frozen in liquid nitrogen. Samples for histochemical procedures were fixed in 10% neutral buffered formalin, included in paraffin wax and treated with polyclonal rabbit anti-APLN and anti-APLNR antibodies (2). Positive staining for APLN and APLNR were observed in the ovary corpus luteum. RT-PCR evidenced both transcripts in the examined organs. As the genital tract concerns, the highest levels were detected in the Cnt group ewes in the luteal phase compared to the MxF group in the anoestrous phase. APLN was detected in the epithelium lining the ampulla and uterus and in the uterine glands. APLNR was showed in the ampulla secreting cells, in the epithelium lining the uterus and uterine glands. APLN showed a high expression in the Cnt group compared to Exp one. The distribution and expression of the apelin system in the reproductive apparatus suggest its involvement in the ewe reproductive functions. Differences evidenced could be mainly related to the cyclic activity of organs, that seems to be affected also by the diet. Data suggest that a more energetic diet can anticipate the beginning of the oestrous cycle.