Human oviductal fluid proteins. V. Identification of human oviductin-I as alpha-fetoprotein.

OBJECTIVE

To investigate whether human oviductin-I (hOV-I) from human oviductal fluid (hOF) and human alpha-fetoprotein (hAFP) are identical molecules.

DESIGN

Comparison of amino acid and carbohydrate composition of hOV-I with that of hAFP. Isolation of hAFP from oviductal fluid of a patient and evaluation of its immunochemical properties in relation to hOV-I and authentic hAFP standard.

SETTING

Procedures were performed in an academic research environment.

PATIENTS

Human oviductin-I was isolated from a pooled sample of hOF obtained from four patients in a third world country. AFP was purified from a sample of oviductal fluid obtained from a single patient during her periovulatory period.

INTERVENTIONS

Human oviductal fluid was collected coincident to elective tubal ligations.

MAIN OUTCOME MEASURES

The amino acid and carbohydrate composition of hOV-I was determined. AFP was purified from hOF using ion-exchange chromatography and gel filtration. The identity between hOV-I and hAFP from hOF was assessed using enzyme-linked immunosorbent assay (ELISA) and Western immunoblot analysis.

RESULTS

The amino acid and carbohydrate composition of hOV-I indicated similarities between hOV-I and hAFP. Both hOV-I and hAFP reacted with mouse anti-hAFP monoclonal antibody and purified polyclonal rabbit anti-hOV-I immunoglobulin G in an identical manner as observed by noncompetitive ELISA. Purified AFP from hOF of a single patient had a molecular mass of 66 kd and was found to be identical with hOV-I by Western immunoblot analysis.

CONCLUSIONS

Human oviductin-I and hAFP are chemically similar and immunologically identical molecules. We believe that this finding is the first documentation for the existence of AFP in hOF.