Itiswellknownthatduringmammalianovarianfolliculardevelopment,themajorityoffolliclesundergoatresiaatvariousstagesoftheirdevelopment.However,themechanismscontrollingthisselectionprocessremainunknown.Inthisstudy,weinvestigatedapoptosisingranulosacellsduringgoatfollicularatresiabyterminaldeoxynucleotidyltransferase-mediateddUTPnickendlabeling(TUNEL).Thechangesinthelevelsofsteroids,insulin-likegrowthfactors(IGFs)andIGFreceptorswerestudiedbyradioimmunoassay(RIA)andsemi-quantitativereversetranscription-PCR.Wefoundthatthepercentageofapoptoticgranulosacellsintheatretic(A)follicleswassignificantlyhigherthanthatintheslightlyatretic(SA)andhealthy(H)follicles.ThelevelofestradiolandtheratioofestradioltoprogesteroneinHfolliclesweresignificantlyhigherthanthoseinAfollicles.Ontheotherhand,thelevelofprogesteronewasnotsignificantlydifferentamongthesefollicletypes.WealsofoundthatthelevelofIGF-IinHfollicleswashigherthaninSAandAfollicles,whereastheamountofIGF-Ⅱdidnotvarysignificantly.TheexpressionofIGFreceptoralsodecreasedinAfolliclesascomparedtothatinHandSAfollicles.TheseresultssuggestedthatestradiolandIGF-Imightbeinvolvedincontrollingapoptosisingranulosacellsduringfollicularatresia.
