title: Effect of exogenous insulin and fasting on growth hormone receptor and IGF-I expression in the pre-ovulatory follicle of ewes.
abstract: The aim of this study was to investigate the effect of fasting and exogenous insulin administration on the expression of growth hormone receptor (GHR) and IGF-I mRNA in the pre-ovulatory follicle of ewes. Fifteen ewes received an intravaginal progesterone releasing device that was removed 6 days later (day of removal = day 0). On day -2, the ewes were divided into three groups: (i) fasting group (n = 5) that was fasted from day -2 to day 2; (ii) control group (n = 5) that received a maintenance diet; and (iii) insulin group (n = 5) that received insulin injections (0.25 IU/kg) every 12 h from day -2 to day 2 under the same diet as the control group. Follicular samples were obtained on day 2. Fasting increased plasma non-esterified fatty acids concentrations from day -1 to day 2 (P < 0.001). There was no difference (P > 0.05) in the number of follicles, although there was a tendency for an increase in the pre-ovulatory follicle diameter for the insulin group in comparison to the control group (P = 0.12). Thecal GHR mRNA expression was very low and was considered insignificant. Moreover, granulosa cells GHR mRNA expression increased (P < 0.05) in the insulin group. Expression of IGF-I mRNA was not different among groups in both tissues. In conclusion, insulin administration increases GHR mRNA but not IGF-I mRNA expression in granulosa cells of the pre-ovulatory follicle. However, fasting did not change the pattern of GHR/IGF-I mRNA expression in the pre-ovulatory follicle.
authors.affiliation: 1Biotechnology Center, Federal University of Pelotas, Campus Universitário, CEP 96010-900, Pelotas, RS, Brazil.
authors.forename: A
authors.initials: A
authors.lastname: Schneider
authors.forename: L F M
authors.initials: LF
authors.lastname: Pfeifer
authors.forename: J W
authors.initials: JW
authors.lastname: da Silva Neto
authors.forename: L T
authors.initials: LT
authors.lastname: Hax
authors.forename: M M
authors.initials: MM
authors.lastname: Antunes
authors.forename: F A B
authors.initials: FA
authors.lastname: Del Pino
authors.forename: G R
authors.initials: GR
authors.lastname: Paludo
authors.forename: M N
authors.initials: MN
authors.lastname: Corrêa