ENDOTHELIUM OF HUMAN UMBILICAL BLOOD-VESSELS - ULTRASTRUCTURAL IMMUNOLOCALIZATION OF NEUROPEPTIDES

Endothelial cells of human umbilical vein and artery, both in situ and in culture, were examined ultrastructurally and at the light-microsco pe level using either the pre-embedding peroxidase-antiperoxidase or a vidin-biotin peroxidase complex immunostaining techniques. Vasoactive intestinal polypeptide (VIP), substance P (SP), calcitonin gene-relate d peptide (CGRP) and arginine-vasopressin (AVP) immunoreactivity were localized in subpopulations of endothelial cells of the term umbilical vein and artery. The percentage of VIP-, SP-, CGRP- and AVP-immunorea ctive cells in the umbilical vein was 12, 10, 11, and 7.5%, respective ly, out of a total of 5,364 cells (from 15 umbilical cords) examined. The artery contained fewer VIP-, SP-, and CGRP-immunoreactive cells, b ut more AVP-immunoreactive cells, than the vein. In conclusion, subpop ulations of endothelial cells in the human umbilical vein and artery c ontain the neuropeptides VIP, SP, CGRP and AVP, although their physiol ogical roles are not yet known.