c-Kit-immunopositive cells in the subendothelium of bovine pulmonary arteries: morphological characteristics and role in vasomotion A. Tracey, V.R. Alapati, A. MacDonald, I.C. Wilkie, R.A. Davidson, A.D. Corbett & A.M. Shaw. Department of Biological & Biomedical Sciences, Glasgow Caledonian University, Glasgow. G4 OBA.	Print Abstract Search PubMed for: Tracey A Alapati VR MacDonald A Wilkie IC Davidson RA Corbett AD Shaw AM

Interstitial cells of Cajal (ICCs) are thought to mediate slow wave vasomotion in the gut (Sanders 1996). The aim of the present study was to investigate the presence of ICCs in bovine pulmonary arteries and their possible role in the vasomotion induced by the thromboxane-mimetic U46619.

Bovine lungs (either sex) were obtained fresh from the local abattoir. Ring segments of conventional arteries (0.3-0.5 cm in diameter, dissected from the 3,^rd and 4^th arterial generation) were mounted in organ baths. In some artery rings the intima was removed by abrading the luminal surface with forceps. The tissues were allowed to equilibrate for 1 hour before the addition of U46619 (5-15 nM). Tissues were prepared for immunohistochemistry and transmission electron microscopy using routine methods. Immunohistochemical studies employed the avidin-biotin immunoperoxidase technique. Sections (5 µm thick) were exposed to the primary antibody (c-Kit, Oncogene, 1:100 dilution) for 1 hour at 37^oC, rinsed and exposed to the secondary antibody, which was a 2% biotinylated goat anti-rabbit antibody (Vector Laboratories).

Discrete c-Kit-like immunoreactivity was detected in association with cells in the subendothelial connective tissue of the conventional arteries. Ultrastructural studies identified elongated cells adjacent to the endothelial cell basal plasma membrane that had long branching cytoplasmic processes.

These interstitial cells contained nuclei, which were oval in outline, had caveolae and cytoplasmic organelles that included numerous mitochondria, rough endoplasmic reticulum and intermediate filaments (approx. 10 nm in diameter). The presence of a basal lamina suggests that these cells are not fibroblasts. The absence of thick and thin filaments, smooth endoplasmic reticulum and membrane-associated dense bands suggests that these cells are distinct from smooth muscle cells. Processes from the basal plasma membrane of the endothelial cell descend to contact, or come close to, the cytoplasmic branches of the interstitial cells. In addition, the interstitial cell processes are found closely apposed to putative nerve terminals that are observed in close association with the basal plasma membrane of the endothelial cell.

U46619 (5-15 nM) but not 5-HT (10 pM-1 µM) induced vasomotion. The rhythm was continuous with a frequency of 1.5 Hz. The contractile phase reached a maximum within 20-30 sec. Mechanical abrasion of the intima converted the vasomotion into a sustained contraction and abolished bradykinin (100 nM)-induced relaxation.

This study suggests that cells in the subendothelium of bovine pulmonary conventional arteries express the c-Kit receptor, have the morphological characteristics of ICCs (Thuneberg, 1982) and may have a role in mediating the vasomotion induced by U46619.

Sanders, K.M. (1996). Gastroenterology, 111, 491-515.
Thuneberg, L. (1982). Adv. Anat. Embryol. Cell Biol., 71, 1-130.