Calcitonin gene-related peptide (CGRP)-immunoreactive nerve fibres and receptors in the human processus vaginalis

Summary

Inguinal hernia is the most common congenital disease in paediatrie surgery. It is apparent that inguinal hernias result from a patent processus vaginalis (PV). However, it remains unclear how the PV closes in normal development. It is proposed that calcitonin gene-related peptide (CGRP) released from the genitofemoral nerve acts on the PV and causes fusion. The aims of this study are to determine whether there are CGRP containing nerve fibres and CGRP receptors in the PV. Immunoreactivity for CGRP was studied in wholemount preparations and frozen sections used for receptor studies. In all 13 PV specimens CGRP-immunoreactive nerve fibres were detected and these nerve fibres were located in the mesenchyme of the PV. A [¹²⁵I] radiological binding assay was performed in 12 hernial sacs to demonstrate the presence of CGRP receptors. Seven of 12 hernial sacs showed specific binding by computerized densitometry in the mesenchyme adjacent to the lining epithelium of the PV. Specific binding ranged from 0.95% to 59.6% of total binding (mean 22.75). Emulsion autoradiography showed [¹²⁵I] labelled CGRP binding to blood vessels and mesenchyme fibroblasts. These findings are consistent with CGRP being released from nerve fibres and binding to CGRP binding sites in the hernial sac.