| Our experiments studied the effects of heat stress on oxidative indexes in mice ovaries and we cultured the primary granulosa cells(GCs)to studied the effects of heat treatment at 40 ? or 43 ? on GCs apoptosis,GCs steroid hormone secretion and the mRNA expression of steroid hormone-related genes(Star,CYP11A1 and CYP19A1).Besides,we detected the cAMP content and the mRNA expression of FSHR in GCs to see whether the FSHR/cAMP/PKA pathway is a heat stress pathway or not.The objective of this study was to reveal the function mechanism of heat stress in ovaries and to provide some references for the study of heat stress on female animals.1 Effects of heat stress on ovary antioxidant capacityThe objective of this study was to determine whether heat stress will cause ovarian injury.Heat stress:36 mice were randomly divided into two groups and the treatment group was placed in 42 ? humidity of 60%of artificial climate chamber and were monitored rectal temperature,they were timed for 30mins when the temperature rose to 40 ?.After that,they were put back in previous environment and then were taken ovarian samples after 6h.Total antioxidant capacity(T-AOC),glutathione peroxidase(GSH-Px)and malondialdehyde(MDA)were determined.Our data showed T-AOC and GSH-Px significantly decreased(P<0.05)while MDA significantly increased(P<0.05),which illustrated ovarian injury was occurred.2 Effects of heat treatment on GCs apoptosisGCs are crucial cells in ovary since they regulate the growth,differentiation and maturation of theca cells and oocytes via synthesizing steroid hormones and growth factors,expressing receptors and transporting small molecules like amino acids and nucleotides.GCs apoptosis and the expression level of apoptosis-related genes(caspase-3,Bax,Bcl-2)were studied after heat treatment.Our data showed,heat induced the GCs apoptosis and increased the expression of caspase-3.However,it had different effects on the mRNA expression of Bax and Bcl-2.Our data illustrated,heat induced the apoptosis of GCs,Bax might play an important role in heat-induced GCs apoptosis while Bcl-2 might not be such important as Bax.3 Effects of heat treatment on GCs steroid hormone secretion and the mRNA expression of steroid hormone-related genes(Star,CYP11A1 and CYP19A1)Estradiol(E2)and progesterone(P4)are the main steroid hormones secreted by GCs.They modulate GCs apoptosis and play an important role in regulating follicular development and follicular atresia.Therefore,the ovarian function will be affected if steroid hormones secretion level changes.RIA(Radio immunity assay)was used to measure the secretion of E2 and P4.RT-PCR was used to evaluate the expression of steroids-related genes(Star,CYP11A1,CYP19A1).Our data suggested that heat stress decreased E2 and P4 secretion and reduced the steroids-related genes mRNA expression,which illustrated heat treatment disturbed GCs steroid hormone secretion and P4 might be more sensitive to heat.4 Effects of heat treatment on FSHR/cAMP/PKA pathway in GCsFSH promotes ovarian growth,follicular growth and ovulation and its role have to be mediated by FSHR.As GCs are the only kind of cells which express FSHR in ovary,they are essential for FSH.The cAMP/PKA pathway is a classic signal pathway.Its processing is as follows:the content of cAMP increases or decreases after signals are transmitted to AC by Gi or Gs,then the activity of protein kinase A changes.Protein kinase A regulates the intracellular biological reaction and it is responsible for the phosphorylation of many proteins like receptors,ion channels and transcription factors.Thus FSH/cAMP/PKA pathway in ovary should be paid more attention since it is optimization of FSH function.Our data showed the content of cAMP and the mRNA expression of FSHR decreased significantly(P<0.05)after heat treatment,which illustrated FSHR/cAMP/PKA pathway played a role in heat-induced apoptosis and secretory dysfunction in GCs. |
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