Beta microseminoprotein is not a prostate-specific protein. Its identification in mucous glands and secretions.

Beta microseminoprotein (beta inhibin, PSP94), an unglycosylated protein of 94 amino acids with unknown function, is one of the predominating proteins in the secretion of the human prostate gland. In this work the authors have demonstrated that the expression of beta microseminoprotein is not restricted to the prostate and that the protein has a previously unrecognized widespread occurrence in the human body. According to radioimmunoassay, beta microseminoprotein immunoreactivity is present in many nonprostatic body fluids. The highest concentrations were found in secretions from the respiratory tract; in tracheobronchial fluid sometimes even at concentrations comparable to that in seminal plasma (about 1 g/l). Intermediate concentrations were found in gastric juice and some samples of secretion from the uterine cervix, whereas tears, saliva, pancreatic juice, bile, and mucus from the colon had low concentrations. According to gel chromatography, the molecular size of the beta microseminoprotein immunoreactivity present in tracheal fluid, gastric juice, and secretion from the uterine cervix did not differ from that of beta microseminoprotein in seminal plasma. The beta microseminoprotein immunoreactive component present in gastric juice had the same amino-terminal amino acid sequence as prostatic beta microseminoprotein (14 residues identified in material purified from gastric juice), providing further evidence for chemical identity of a nonprostatic beta microseminoprotein with the prostatic protein. Immunohistochemical staining with affinity-purified antibodies demonstrated the presence of beta microseminoprotein in many tissues, including the goblet cells in the tracheobronchial epithelium, tracheobronchial submucosal glands, certain mucosal cells in the antrum of the stomach, some glands of Brunner in the duodenum, and in parts of the mucosa of the colon. At least in the respiratory tract, the staining was localized to mucus-containing cells. beta microseminoprotein immunoreactivity also was localized to the cilia of the ciliated epithelium in the respiratory tract, the fallopian tubes, and the Gartner ducts of the uterine cervix. The pattern of tissue distribution of beta microseminoprotein found in this work indicates a connection of beta microseminoprotein with mucous secretions.

Radioimmunoassay of beta-microseminoprotein, a prostatic-secreted protein present in sera of both men and women.

We describe a simple radioimmunoassay of beta-microseminoprotein, one of the three most abundant secretory proteins of the prostate gland. The detection limit of the assay is 1 microgram/L, and its precision, expressed as the total coefficient of variation, is less than 10% for values between 10 and 150 micrograms/L. Using this assay, we found that beta-microseminoprotein immunoreactivity was present in sera from both sexes at about the same concentration. The protein detected had the same molecular size on gel chromatography as the protein isolated from seminal plasma, and dilution curves for the sera paralleled that for the pure protein. The findings suggest that beta-microseminoprotein is present in serum of healthy subjects of both sexes and that it originates in tissue other than the prostate gland. The range of the serum concentration was 0-10.6 micrograms/L (median 4.1) for 51 healthy adult women and 1.1-14.7 micrograms/L (median 6.2) for 35 healthy adult men not older than 40 years. In males with prostatic cancer the concentration in serum was highly variable and often greatly increased. The concentration of beta-microseminoprotein was correlated with that of creatinine in serum, suggesting that the protein is eliminated--at least partly--from the circulation by glomerular filtration. Little of the protein was present in the urine of women. In urine from men the concentration was high and variable, probably because of local contribution from the prostate gland to the urethral urine.

A new sensitive immunosorbent radioassay for the detection of circulating antibodies to polypeptide hormones and proteins.

A solid-phase immunosorbent radioassay for the detection of circulating antibodies to protein hormones is described. The assay is based on the binding of the homologous 125I-labelled antigen to the antibodies which are then bound to anti-IgG antibodies covalently coupled to Sepharose. It can easily be applied as a complement to any radioimmunoassay for the detection of circulating antibodies to the ligand measured. The assay system avoids falsely elevated values due to interference of high serum concentrations of the antigen. The assay was applied to measure antibodies to FSH, LH, TSH, GH, prolactin, insulin and thyroglobulin (Tg). Among patients with chronic thyroiditis Tg antibodies were found in 100% of the sera. In diffuse toxic goitre 73% of the patients had detectable Tg antibodies. Insulin antibodies were present in 82% of the sera from patients with insulin treated diabetes. No antibodies were found against the other protein hormones tested.