Avaliação da vascularização e da angiogênese de corpos lúteos de éguas com ovulação natural e induzida por acetato de deslorelina

Abstract

Much has been made in order to enhance the implementation and improve results of assisted reproductive biotechnologies in mares, however there are still few studies on vascularization of the corpus luteum (CL) and its relation to progesterone and angiogenic factors and their consequences when the ovulation is induced with deslorelin acetate. Mares were used in natural ovulation (GC) condition and induced (GT) with deslorelin (>35 mm follicles). In the experiment 1 ovulation and CL formation were followed by Doppler ultrasound (6.5 MHz), on days 4, 8 and 12 after ovulation (D0). Blood samples were obtained for progesterone assay by enzyme-immunoassay. The CLs were analyzed for vascularization, and images were recorded in video. Image analysis considered the percentage of luteal parenchymal area presenting color signals. The results were presented as mean ± epm. The average vascularization was in GC: 76.25 ± 8.98; 70.00 ± 8.16 and 57.50 ± 13.31 % and in GT: 85.00 ± 5.40, 90.00 ± 0.00 and 58.75 ± 9.24 % respectively for the days 4, 8 and 12 after ovulation. Progesterone concentrations were in GC: 6.21 ± 0.61; 5.82 ± 1.44 and 4.63 ± 0.79 ng/mL and GT: 6.10 ± 1.18; 4.67 ± 1.06 and 4.49 ± 1.37 ng/ml, respectively for the 4, 8 and 12 days after ovulation. The patterns of vascularization were higher in D4 and D8 compared to D12 of GT (P<0.05). However, there were no differences between groups or days in GC. The concentration of progesterone didn’t show significant differences between groups or studied days. In experiment 2, samples of CL were collected through ultrasound guided biopsy at the same time points after ovulation. The mRNA expression of VEGF, BFGF and LHR genes were analyzed by real time PCR. It was observed positive correlation between VEGF and LHR (P < 0.00001, r = 0.78), and it was possible to detect a higher LHR expression in D4 of GT than GC (p < 0.05), moreover this expression was higher in D4 and D8 than D12 of the GT group. bFGF was also expressed in luteal tissue in all days of both groups, however without statistical differences. It was concluded that deslorelin acetate was effective to induce ovulation in mares which did not alter the physiological responses of the corpus luteum in respect of the plasma progesterone concentration, however, affected luteal parenchyma vasculature. Also, LHR and VEGF expression was influenced by induced ovulation, with a lower level at D12, what must be expected in non-pregnant mares.