Evaluation of steroidogenic capacity after follicle stimulating hormone stimulation in bovine granulosa cells of Revalor 200 implanted heifers

摘要

Background:Heifers not used as breeding stock are often implanted with steroids to increase growth efficiency thereby altering hormone profiles and potentially changing the environment in which ovarian follicles develop.Because bovine granulosa cell culture is a commonly used technique and often bovine ovaries are collected from abattoirs with no record of implant status,the objective of this study was to determine if the presence of an implant during bovine granulosa cell development impacts follicle stimulating hormone-regulated steroidogenic enzyme expression.Paired ovaries were collected from 16 feedlot heifers subjected to 1 of 3 treatments:non-implanted(n = 5),Revalor 200 for 28 d(n = 5),or Revalor 200 for 84 d(n = 6).Small follicle(1 to 5 mm)granulosa cells were isolated from each pair and incubated with phosphate buffered saline(n = 16) or 100 ng/mL follicle stimulating hormone(n = 16) for 24 h.Results:Granulosa cells of implanted heifers treated with follicle stimulating hormone produced medium concentrations of progesterone similar(P = 0.22) to non-implanted heifers,while medium estradiol concentrations were increased(P<0.10) at 28 and 84 d compared to non-implanted heifers indicating efficacy of treatment.Additionally,real-time PCR analysis in response to follicle stimulating hormone treatment demonstrated a decrease in steroidogenic acute regulatory protein(P = 0.05) mRNA expression in heifers implanted for 84 d and an increase in P450 side chain cleavage mRNA in granulosa cells of heifers implanted for 28(P< 0.10) or 84 d(P< 0.05)compared to non-implanted females.However,no difference in expression of 3-beta-hydroxysteroid dehydrogenase(P = 0.57) and aromatase(P = 0.23) were demonstrated in implanted or non-implanted heifers.Conclusions:These results indicate follicles which develop in the presence of high concentrations of androgenic and estrogenic steroids via an implant tend to demonstrate an altered capacity to respond to follicle stimulating hormone stimulation.Thus,efforts should be made to avoid the use of implanted heifers to study steroidogenesis in small follicle granulosa cell culture systems.