02865naa a2200337 a 450000100080000000500110000800800410001902400330006010000200009324501260011326000090023952019610024865000100220965000170221965000090223665000170224565000100226265000140227265300170228665300080230365300150231165300070232665300190233365300210235265300190237370000200239270000130241270000180242570000170244377300670246020712962017-06-22       1989    bl uuuu     u00u1 u    #d7 a: 10.1677/joe.0.12002952DOI1 aMcNEILLY, A. S.  aChanges in the plasma concentrations of inhibin throughout the normal sheep oestrous cycle and after the infusion of FSH.  c1989  aAbstract: A radioimmunoassay for inhibin was developed using a peptide containing the 1-26 amino acid sequence of the N-terminus of the alpha-chain of 32 kDa porcine inhibin as immunogen, and 125I-labelled tracer. Evaluation of this assay using Sephadex column chromatography, chromatoelectrophoresis and immunoblotting confirmed that it measured all forms of inhibin present in sheep follicular fluid and was suitable for measurement of inhibin in sheep plasma. There was no evidence of the presence of free alpha-subunit in either sheep follicular fluid or ovarian vein plasma. The concentration of inhibin in jugular plasma throughout the follicular and luteal phases of four ewes with ovarian autotransplants was measured. The ovarian secretion of inhibin and oestradiol were also measured simultaneously throughout the follicular phase in a spontaneous cycle and after infusion of NIH-oFSH-S14 at 10 micrograms/h for 48 h following premature luteal regression induced by prostaglandin. The results showed: (1) no change in the peripheral concentration of inhibin throughout the cycle except an increase related to the periovulatory increase in FSH and LH. (2) Following luteal regression, the concentration of FSH fell as the secretion rate of oestradiol increased. During this time there was no significant change in the peripheral concentration of inhibin or ovarian inhibin secretion rate. (3) Following the infusion of FSH there was a marked increase in the concentration of inhibin in both ovarian and peripheral plasma and an increase in ovarian inhibin secretion rate. (4) The calculated metabolic clearance rate of inhibin, 20.3 ml/min, is similar to that of FSH. We conclude that in the ewe the ovarian inhibin secretion rate is stimulated by FSH and, although inhibin may modulate the basal secretion of FSH, a change in its secretion does not account for the fall in FSH which occurs during the follicular phase of the sheep oestrous cycle.  aBlood  acloprostenol  aEwes  aPharmacology  aSheep  aEstradiol  aDrug effects  aFSH  aInhibition  aLH  aOestrous cycle  aRadioimmunoassay  aSecretory Rate1 aSWANSTON, I. A.1 aCROW, W.1 aTSONIS, C. G.1 aBAIRD, D. T.  tJournal of Endocrinologygv. 120, n. 2, p. 295-305, Feb. 1989.