Calcitonin in human seminal plasma and its localization on human spermatozoa

We determined the calcitonin (CT) levels in peripheral plasma and in seminal fluid of 15 normal human subjects: the concentration of the hormone in seminal fluid was about 30 times higher than the concentration found in peripheral plasma. We also studied the localization of calcitonin on human spermatozoa by means of an indirect immunofluorescent technique, using an anti-human CT rabbit serum and a fluorescein-isothiocyanate conjugated goat anti-rabbit immunoglobulins serum. A bright fluorescence was observed at the middle piece and neck, while the tail's principal piece was weakly stained. With an anti-human CT rabbit serum pre-absorbed with human CT no fluorescent staining was detectable. These findings demonstrate that calcitonin is localized onto spermatozoa and suggest a potential role for calcitonin in the calcium dependent-mechanisms of spermatozoa.