Pregnancy-Associated Plasma Protein A in Human Ovarian Follicular Fluid

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Abstract
Human ovarian follicular fluid contains pregnancy-associated plasma protein A (PAPP-A) immunoreactivity as detected by RIA. This PAPP-A was found to be stable to repeated freeze-thaw cycles and not removed by dialysis. Further characterization showed that ovarian follicular PAPP-A bound reversibly to heparin-Sepharose. On gel chromatography follicular PAPP-A coeluted with radioiodinated PAPP-A and pregnancy serum PAPP-A which was determined to have an apparent molwt of 820,000. In the RIA, serial dilutions of high molecular weight heparin-Sepharose binding proteins gave parallel displacement curves to pooled late pregnancy serum and to the International Reference Preparation, WHO 78/610. All the human ovarian follicular fluids tested had PAPP-A concentrations between 0.317-1.595 IU/liter. The relationship between follicular content of PAPP-A and follicular volume was best expressed by the exponential relationship, y = 164.3 e0117x. Therefore,ovarian follicular fluid PAPP-A has many physico-chemical similarities to and shares immunologicalidentity with pregnancy-derived PAPP-A. As this pregnancy-associated glycoprotein cannot be detected in the circulation of normal non-pregnant adults, its presence within the Graafian follicle isbelieved to be of intrafollicular origin for the maintenance of proteolytic homeostasis.