148 In vivo administration of propranolol induces follicular activation in mice

The ovarian reserve consists of the number of primordial follicles in a quiescent state and only a few primordial follicles are activated for the growth phases. Activation and quiescence of primordial follicles are controlled by signalling pathways, among which PI3K/AKT/mTOR is the most studied, with mTOR (mammalian-target of rapamycin) expressed in all follicle stages. Propranolol is described in the literature as activating mTOR in different types of cells, and an in vitro study showed that propranolol can promote primordial follicle activation in mouse and human ovarian tissues. In this scenario, the objective of the present study was to evaluate the effect of propranolol on follicular activation in pre- and post-pubertal female C57BL6 mice. The experiment was divided into two; in the first experiment, the treatment was carried out at different ages: (A) from the fourth to the sixth week and (B) from the sixth to the tenth week. For each experiment, the animals were divided into three groups: Control (n = 6), Low (n = 6), and High (n = 6). The animals in the control group received the vehicle (PBS), those in the Low group received a dose of 15 mg/kg, and those in the High group received a dose of 40 mg/kg, all administered intraperitoneally every day (at age A, applied during the fourth through sixth week; at age B, applied during the sixth through tenth week). In this first experiment, at the end of the experimental period, the ovaries were collected and destined for follicular quantification. In the second experiment, the analysis of superovulation was performed, and the animals of age A (from the 4th to the 6th week) were divided into three groups: Control (n = 10), Low (n = 10), and High (n = 10), and received the same doses described previously. They were superstimulated with 20 IU of equine chorionic gonadotrophin (eCG) after 48 h 20 IU of human chorionic gonadotrophin (hCG); after 13 h, the ovulated oocytes were collected and quantified. All quantitative data were tested for normality using the Shapiro-Wilk tests. Parametric data were tested by ANOVA, followed by the Newman-Keuls test. All statistical analyses were performed in GraphPad (GraphPad Software Inc.) and data are shown as mean ± s.e.M. A decrease in the number of primordial follicles (223 ± 32 Control, 171 ± 23 Low, 145 ± 20 High; P = 0.03) and an increase in the number of primary follicles (18 ± 5 Control, 30 ± 7 Low, 57 ± 18 High; P = 0.007) in animals at six weeks were observed. The follicular activation rate (n growing follicles ÷ n total healthy follicles × 100) in six-week-old animals increased compared to control (19.11 ± 4 Control, 34.3 ± 2 Low, 41.4 ± 2.6 High; P = 0.0004). There was no significant difference in the follicle population at 10 weeks; however, the activation rate was significantly increased in the treatment in relation to the control (48.7 ± 2 Control, 54 ± 3 Low, 61 ± 2.5 High; P = 0.01). In the superovulation assay, there were no significant differences between groups (3.8 ± 0.5 Control, 3.5 ± 0.3 Low, 3.8 ± 0.6 High; P = 0.54). In general, our findings indicate that propranolol acts in the activation of primordial follicles in pre-pubertal females; however, this effect was attenuated in post-pubertal animals.

This research was supported by CAPES, FAPEMIG, and CNPq.