Diferentes ofertas de água e de leptina e seus efeitos na foliculogênese no semiárido pernambucano

Abstract

The present study evaluated the effect of different levels of water supply and leptin on the folliculogenesis of crossbred Santa Inês sheep (Experiment I), and the effect of leptin on the in vitro culture of early antral follicles isolated from mixed-breed sheep (Experiment II). In the first experiment, 32 ewes (n = 8 ewes per treatment) were submitted to different levels of water supply: 100% water (ad libitum - control) and 80%; 60% and 40% of water supply from the control group's water intake for 63 days. Blood was collected for the determination of estradiol and progesterone. At the end of the experiment, the sheep were weighed, slaughtered and their ovaries and uteri were weighed. The ovaries were used for histological analysis of the ovarian cortex; in vitro maturation (IVM) of oocytes from antral follicles grown in vivo; or the in vitro culture of secondary follicles isolated in the absence (α-MEM+) or in the presence (10 and 25 ng/mL) of leptin, for 12 days. In experiment II, 50 pairs of mixed-breed sheep ovaries were destined for the in vitro culture of early antral follicles isolated in medium supplemented with leptin concentrations (0, 2 and 10 ng/mL), for 12 days. At the end of the culture, oocytes were destined for IVM and later for the analysis of mitochondrial activity and reactive oxygen species (ROS). The water supply of 40% reduced the survival of preantral follicles, especially of primordial follicles (P <0.05). The concentration of 25 ng/mL of leptin showed a larger follicular diameter, total and daily growth rate of sheep follicles that had a 40% reduction in water supply (P <0.05) compared to follicles grown on α-MEM+. The concentration of 2 ng/mL leptin resulted in a higher percentage of morphologically normal follicles, fully grown oocytes, resumption of meiosis and active mitochondria levels when compared to the control medium (TCM 199+; P <0.05), but did not differ when compared to 10 ng/mL leptin (P> 0.05). In conclusion, the water supply of 40% reduces the survival in situ of preantral follicles, mainly of primordial follicles. Leptin (25 ng/mL) stimulates the in vitro growth of secondary follicles isolated from sheep subjected to 60% water supply and, at a dose of 2 ng/mL, improves the survival of antral follicles, oocyte growth, mitochondrial activity and the resumption of meiosis after the in vitro culture of isolated sheep early antral follicles.