Localisation of VIP- and CGRP-like substances in the skin and sinus hair follicles of various mammalian species

Abstract

Using an ultrastructural postembedding immunogold technique, we demonstrated vasoactive intestinal polypeptide (VIP)- and calcitonin gene-related peptide (CGRP)-like immunoreactivity in the Merkel cell dense-cored granules of skin and sinus hair follicles of adult cat and dog. The VIP-like substance was located in cat Merkel cells while both VIP- and CGRP-like substances were colocalised in dog Merkel cells. In cat Merkel cells, the magnitude of labelling of VIP was qualitatively higher than in dog Merkel cells. In the dog Merkel cell, CGRP appeared as the most abundant peptide. Dense-cored granules were labelled for these peptides. In addition, mast cells encountered in the dermal region of dog skin were also found to be immunolabelled by VIP antiserum. The immunoreaction was found to be confined to the secretory granules of the cells. Furthermore, all non-myelinated nerve plexuses encountered in the dermal region of the skin and the sinus hair follicles of the various mammalian species studied were immunolabelled by CGRP antiserum. The specific location was again restricted to the dense-cored granules present in these nerves. As VIP and CGRP have potent vasodilatory effects, our observations suggest that Merkel cells may play a separate or synergistic role in regulatory functions of the skin neuroendocrine cell, exerting their influence by paracrine, endocrine and neurocrine pathways, or a combination of these. Different methodologies of double labelling with different sizes of gold particles are also discussed.

Merkel cells

“…18 The function of noninnervated MCs is still unknown. Like innervated MCs, they synthesize numerous polypeptides and their receptors, which strongly suggests paracrine or autocrine communication, [128][129][130] such as regulatory functions associated with the metabolism of cutaneous cells. The skin contains an equivalent of the hypothalamus-pituitary-adrenal axis, leading to the suggestion that the cutaneous neuroendocrine system communicates through humoral and neural pathways to regulate the vascular, immune, or pigmentary systems.…”

The role of mast cells in atopy: what can we learn from canine models? A thorough review of the biology of mast cells in canine and human systems

“…Moreover, we and others 153,154 have shown that SCF used as a cell growth promoter and a costimulator enhances the ability of mast cells to release TNF‐ α , an effect that has also been reported in relation to human mast cell mediators 155 . Other cytokines have been shown to be expressed by both canine and human mast cells 156–158 . Notably, Sinke et al 159 reported the production of IL‐4.…”

Recent progress in studies on Merkel cell biology

“…Some immunocytochemical studies have shown that these substances exist in MC granules (Weihe et al. , 1991; Cheng Chew & Leung, 1991, 1994, 1996; Hartschuh & Weihe, 1988). It is likely that these substances coexist with chromogranin A (Gauweiler et al.…”