Calcitonin receptor mRNA expression in the human prostate

Objectives. A subpopulation of prostate neuroendocrine (NE) cells contain calcitonin (CT). It has been postulated that CT-producing cells in the prostate account for the high CT level in the semen, and may be involved in the regulation of other epithelial cells via a paracrine mechanism. The presence of CT binding sites in the plasma membrane fraction of prostate tissue has been demonstrated by radioligand binding assay, In the present study, we investigated the CT receptor gene expression in the human prostate, a key component of the autocrine/paracrine loop in the CT functional pathway. Methods. Reverse transcription polymerase chain reaction (RT-PCR) was carried out to evaluate the CT receptor mRNA expression in normal prostate tissue. Subsequent DNA sequencing was used to verify RT-PCR amplified products and to determine the isoform of the receptor. To define the location of the CT receptor expression, nonradioactive in situ hybridization was performed with a digoxigenin-labeled probe complementary to the coding region of the CT receptor mRNA. A polyclonal antibody against CT was used to reveal the CT-secreting cells in the prostate. Results. CT receptor mRNA expression was detected in the prostate tissue, Further analysis of the DNA sequence showed that CT receptor expressed in the prostate was the isoform without a 16-amino acid insert in the first intracellular domain. In situ hybridization revealed that CT receptor was present in the prostate NE cells, Immunocytochemical staining of mirror image sections showed that some CT-secreting cells also expressed CT receptor. Conclusions. CT receptor expression in the prostate, a key component in the CT functional pathway, is located in subsets of dispersed NE cells (CT secreting and CT nonsecreting), which indicates that prostate CT may play an important role in the autocrine/paracrine regulation of the prostate NE system.