Evidence for the existence of a large molecular weight protein in human pituitary tissue having follicle stimulating hormone activity.

A large molecular weight protein fraction was isolated during purification of follicle stimulating hormone (hFSH) from acetone preserved human pituitary glands. This large molecular weight fraction, F-1, was not retarded by Sephadex G-100 as was hFSH, nor did it penetrate 7.5% acrylamide gel upon electrophoresis in sodium dodecyl sulfate as did hFSH. There was no evidence of dissociation of F-1 into smaller molecular weight fractions upon its refiltration through Sephadex G-100 or upon electrophoresis, suggesting F-1 was not an aggregate of smaller size proteins. Fraction F-1 stimulated ovarian growth in rats, inhibited binding of 125I-hFSH to rat testes membranes and cross-reacted with antiserum to hFSH, hFSH-alpha subunit and hFSH-beta subunit as determined by radioimmunoassay. Based on gel filtration experiments, it seemed unlikely that immunologic activity against subunit antisera could be attributed to contamination of F-1 by free FSH subunits. The membrane binding activity of F-1 decreased after incubation with 8M urea, but at a rate less than 1/2 that seen with intact hFSH similarly treated, indicating the two activities were not identical. These results suggest that human pituitary tissue contains a large molecular weight protein with FSH-like biologic and immunologic activity, but which is distinct from native hFSH.