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H Higashimori1 , JF Roser1 *, BL Lasley2 *
Dept of Animal Science, University of California, Davis, CA 1
Dept of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA 2
Inhibin, a glycoprotein hormone consisting of an and subunit linked by disulfide bonds, inhibits the synthesis and secretion of FSH. The prepro-/ subunits undergo post-translational modification resulting in several different molecular weight (MW) forms of inhibin: 1) free / subunits (14-19 kDa), 2) hetero-dimers A/B (31-34 kDa), 3) precursor molecules (25-29 kDa), 4) dimers of the subunits/activins (27-29 kDa) and 5) high MW inhibins (>45 kDa). Little work has been done to isolate, purify and characterize equine inhibin. Consequently, little is know about its physiological role in the horse. The objective of this study was to isolate and purify equine inhibin for reproductive research and diagnostic use. With the aid of a computer sequence analysis package (GCG, Madison, WI), two different highly antigenic amino acid sequences of the -subunit of equine inhibin were selected. The peptides were synthesized (MPS, San Diego, CA) and used to immunize six adult New Zealand rabbits for 10 months. Each antibody was purified by a peptide-conjugated affinity chromatography column. Equine follicular fluid was applied to purified equine inhibin -subunit specific antibodies conjugated affinity column. The material in the eluates cross-reacted with bovine inhibin in a dose response fashion and significantly suppressed secretion of FSH from rat pituitary cells. 12% SDS-PAGE gel separated out the material into six distinct MW bands: 25-26 kDa, 29-30 kDa, 31-34 kDa, 44-45 kDa, and 68 kDa. The 25-26 kDa and 44-45 kDa bands were sequenced and identified as equine inhibin pro--C and N-C peptide, respectively. In conclusion, partial purification of equine inhibin has been accomplished. It appears that equine inhibin exists in different MW forms as has been demonstrated in other species.
This abstract is being presented on Tuesday, August 3 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.