Immunoextracted calcitonin from human seminal plasma constitutes different forms.

Levels of immunoreactive calcitonin (iCT) in human seminal plasma were studied after extraction with immobilized antibodies. Immunoextraction of semen was necessary to abolish the high concentrations of proteolytic enzymes that can interfere in radioimmunoassay (RIA). Since proteolysis occurs already during semen liquefaction, iCT levels and chromatographic properties were compared in extracts from liquefied ejaculates, and samples were the proteolysis was suppressed by immediate dilution of the ejaculates with buffer. The levels in the two groups were 81 +/- 43 pg-equivalents ml-1 seminal plasma (mean +/- SD, n = 6) in liquefied samples and 120 +/- 42 pg-equivalents ml-1 (n = 7) in diluted samples, which is about ten times the iCT levels in extracted blood plasma from healthy males. Extracted liquefied seminal plasma from two vasectomized men contained 93 and 107 pg-equivalents of iCT ml-1 seminal plasma, respectively. Gel chromatography of undiluted semen samples disclosed that iCT was composed of forms larger than monomeric CT, the major part with an approximate molecular weight (MW) of 10,000. Two of the six subjects had a smaller amount of iCT eluting with a MW of about 40,000. In diluted samples, iCT seemed to be more heterogenous with approximate molecular weights ranging from 40,000 to fragments smaller than monomeric CT. In some ejaculates, monomeric CT seemed to be present. Undiluted samples from vasectomized men contained iCT with the same chromatographic pattern as in normal men.