[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"doc-detail-151018-en":3,"doc-seo-151018-105":30,"detail-sidebar-cat-0-en-105":92},{"code":4,"msg":5,"data":6},0,"success",{"doc_id":7,"user_id":8,"nickname":9,"user_avatar":10,"doc_module":4,"category_id":11,"category_name":12,"doc_title":13,"doc_description":14,"doc_content":15,"file_id":16,"file_url":17,"file_type":18,"file_size":19,"view_count":20,"is_deleted":4,"is_public":20,"is_downloadable":20,"audit_status":20,"page_count":21,"language":22,"language_code":23,"site_id":24,"html_lang":23,"table_of_contents":25,"faqs":26,"seo_title":27,"seo_description":14,"update_tm":28,"read_time":29},151018,1374391974585,"Genevieve","https://ap-avatar.wpscdn.com/davatar_276721f389ce27ea32af1340a28f341c",8,"Research & Report","Inhibin and oestradiol in the control of FSH secretion inthe sheep","FSH secretion in sheep is regulated at the anterior pituitary by negative feedback from ovarian hormones, mainly oestradiol and inhibin. Both hormones are produced by granulosa cells of large antral follicles throughout the oestrous cycle, linking follicle differentiation and aromatase activity to hormone output. Oestradiol fluctuations track day-to-day changes in FSH during the follicular phase, while inhibin—with a longer half-life—sets the overall feedback level. This dual control monitors both total large antral follicle numbers and which follicles are selected for ovulation.","# Inhibin and oestradiol in the control of FSH secretion inthe sheep\n\nD.T.Baird,B.K.Campbell,G.E.Mann and A.S.McNeilly*  \nDepartment of Obstetrics and Gynaecology and*MRC Unit of Reproductive Biology,Centre forReproductive Biology,University of Edinburgh,37 Chalmers Street,Edinburgh EH39EW,UK  \nSummary.In the sheep both FSH and LH are necessary for development oflarge antralfollicles.The secretion of FSH is controlled by the negative feedback effect of twoovarian hormones,oestradiol and inhibin,acting at the level of the anterior pituitary.Both are derived from the granulosa cells of large antral follicles which are present insheep ovaries throughout the oestrous cycle.FSH stimulates growth and mitosis and sothe fully differentiated granulosa cells of the large preovulatory follicles acquire recep-tors for LH,have maximal aromatase activity and produce large amounts ofinhibin.The number of these large antral follicles(oestrogenic)which have the poten-tial for ovulation corresponds to the ovulation rate specific for each particular breed ofsheep.Over 90%of the oestradiol secreted by the ovaries is derived from these chosenfollicles.In contrast,inhibin(and androstenedione)is also secreted by large antralfollicles which have lost or not yet acquired maximal aromatase activity.  \nThe secretion of oestradiol by the preovulatory follicle(s)is dependent on the sup-ply of androgen precursors produced by the theca which is stimulated by LH.When theconcentration of progesterone falls at the end of the luteal phase the increased secretionof LH stimulates the progressive increase in secretion of oestradiol which occurs duringthe follicular phase.At this stage of the cycle there is a modest inconsistent rise ininhibin,the secretion of which is not stimulated by LH but is related to the increase inthe number of large antral follicles.Itis suggested that inhibin with its long half-life setsthe overall level of negative feedback while oestradiol is responsible for the day-to-dayfluctuations in the concentration of FSH which determines the number of ovulatoryfollicles.This dual control of FSH is adapted to monitor both the total number of largeantral follicles in the ovaries (inhibin)and the number which are selected for ovulation(oestradiol).  \nKeywords.inhibin;oestradiol;FSH;sheep  \n## Introduction\n\nThe development of antral follicles is dependent on the secretion of pituitary gonadotrophins,asindicated by the absence of healthy antral follicles after hypophysectomy(Dufour et al.,1979).Inthe sheep,large antral follicles develop at all stages of the oestrous cycle but only progress throughthe final preovulatory maturation during the follicular phase(Baird &McNeilly,1981).It isthought that selection of the follicle(s)which will ovulate occurs in the early follicular phase fromamongst the pool of small antral follicles(~2mm in diameter)which are present in the ovaries atthis time.Although the mechanism responsible for this selection is not entirely clear,it probablyinvolves FSH and LH as well as local paracrine factors within the ovary.The fall in the concen-tration of FSH which occurs during the follicular phase plays a key role in limiting the number offollicles which eventually ovulate(Baird,1983).In this paper we shall consider the factors regulat-ing the secretion of FSH throughout the oestrous cycle in the sheep.It is our hypothesis that the  \nconcentration of FSH determines the number of follicles ovulated,and therefore control of itssecretion is a crucial element in reproductive activity in the sheep.  \n## Secretion of FSH\n\nFSH is synthesized in the gonadotrophs of the anterior pituitary,probably in the same cell whichsynthesizes LH.The secretion of both gonadotrophins is stimulated by gonadotrophin-releasinghormone(GnRH),although the synthesis of FSH continues even in the absence of pulsatilestimulation(McNeilly,1988).For example,administration of antiserum to GnRH or a potentantagonist of GnRH results in a rapid and prolonged suppress","cbCaickB5C9tWffs","https://ap.wps.com/l/cbCaickB5C9tWffs","pdf",1236919,1,14,"English","en",105,"# Introduction\n## Secretion of FSH\n## The effect of oestradiol and inhibin on FSH concentration","[{\"question\":\"How is FSH secretion controlled in sheep?\",\"answer\":\"FSH secretion is controlled through negative feedback acting at the anterior pituitary by ovarian hormones, particularly oestradiol and inhibin.\"},{\"question\":\"Where do oestradiol and inhibin come from in the ovarian cycle?\",\"answer\":\"Both are derived from granulosa cells of large antral follicles present throughout the oestrous cycle.\"},{\"question\":\"What roles do oestradiol and inhibin play in regulating FSH over time?\",\"answer\":\"Inhibin sets the overall level of negative feedback due to its long half-life, while oestradiol drives day-to-day fluctuations in FSH concentration during the follicular phase.\"}]","Inhibin and oestradiol in the control of FSH secretion inthe sheep | 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is FSH secretion controlled in sheep?","Question",{"text":76,"@type":77},"FSH secretion is controlled through negative feedback acting at the anterior pituitary by ovarian hormones, particularly oestradiol and inhibin.","Answer",{"name":79,"@type":74,"acceptedAnswer":80},"Where do oestradiol and inhibin come from in the ovarian cycle?",{"text":81,"@type":77},"Both are derived from granulosa cells of large antral follicles present throughout the oestrous cycle.",{"name":83,"@type":74,"acceptedAnswer":84},"What roles do oestradiol and inhibin play in regulating FSH over time?",{"text":85,"@type":77},"Inhibin sets the overall level of negative feedback due to its long half-life, while oestradiol drives day-to-day fluctuations in FSH concentration during the follicular 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