Endothelial cell pavement pattern in the pulmonary trunk in rats in chronic hypoxia

Effects of chronic hypoxia on the secretory responses of rat salivary glands

Female Wistar rats were placed for 3 weeks in a simulated chamber evacuated by a vacuum pump and maintained at 40.5 kPa (7100 m). Dose-response curves were obtained through the sequential injection, via the femoral vein, of increasing doses of methacholine, methoxamine, isoprenaline and substance P. The secretory activity in the parotid gland after exposure to chronic hypoxia was significantly decreased for all agonists studied, and the submaxillary gland showed the same behaviour except in relation to isoprenaline, which did not show a significant difference compared to controls. These data suggest that changes in the number or sensitivity of autonomic receptors and/or alterations in the intracellular signals caused by hypoxia may be involved in the reduction in salivary secretory responses.

A quantitative study of the effects of chronic hypoxia on the histological structure of the rat major salivary glands

Ten young adult female Wistar rats were placed in a decompression chamber at a simulated altitude of 5500 m for 28 days, after which they were killed and their salivary glands and thoracic organs were compared with those of eight matched control rats that had been maintained at sea-level atmospheric pressure. The prolonged hypoxic conditions were severe enough to induce structural changes in the heart and lungs of experimental rats, and their parotid and submandibular, but not sublingual, glands showed severe hyperaemic responses. However, no parenchymal changes occurred in any of the major salivary glands. The mean proportional volume of vascular tissue was increased by 57% in the parotid and 30% in the submandibular glands, and the mean intralobular capillary densities were also increased, by 29 and 18% respectively, in these two glands. The effectiveness of these vascular responses in protecting the salivary parenchymal elements against hypoxic degeneration probably reflects the high reserve potential normally present in salivary blood flow.

Endothelial pavement patterns in human arteries

The endothelium of the carotid arteries, pulmonary trunk and aorta from twelve human subjects aged between 42 and 86 yr was examined en face after staining of the cell borders with a silver nitrate solution. The three vessels each showed similar features with a background pattern of fusiform, mononuclear cells oriented in the longitudinal axis of the vessel. Superimposed on this was a highly variable pattern of small and large polygonal cells and, less commonly, giant cells. Many examples of an abrupt transition from one pattern to another were observed. Preparations which were also stained with haematoxylin showed that large polygonal cells and giant cells contained many nuclei, often arranged into one or more nuclear clusters. The endothelial pattern was related to the underlying intimal structure by taking transverse sections of selected arterial segments. Although a specific endothelial pattern could not be related to a particular intimal morphology, there was a tendency for increasing intimal fibrous thickening and lipid deposition to be associated with more disorganised endothelial patterns and with the presence of large, multinucleate endothelial cells.

Secretory phenotypes of endothelial cells in culture: comparison of aortic, venous, capillary, and corneal endothelium

Endothelial cells from different tissues display variations in morphology, intercellular junctions, cell surface and growth properties, and in production of basal lamina components, both in vivo and in vitro. We have investigated the spectra of extracellular proteins secreted by bovine endothelial cells cultured from large vessels, cornea, and capillaries. Aortic, venous, and corneal endothelial cells displayed highly similar patterns of protein synthesis as judged by analysis of the culture medium; the major products were fibronectin, a glycoprotein similar or identical to platelet thrombospondin, and Type III procollagen. Ion-exchange chromatography, followed by peptide mapping, confirmed the presence of EC, a novel endothelial collagen previously described in bovine aortic endothelial cell cultures. Minor variations were found in the collagens of the cell layers: Type III, the predominant interstitial collagen, was associated with the basement membrane Types IV and V and, in the case of corneal endothelium, with Type I. In contrast, capillary endothelial cells secreted significantly more collagen than did the aortic, venous, and corneal cells. Approximately 50% of the protein in the culture medium was collagenous and consisted of Types I and III collagen in a ratio of 2:3. These interstitial collagens were the only types detected in capillary cell layers as well. The pattern and overall rate of collagen synthesis by capillary endothelial cells in vitro contrasted significantly with that of the other endothelial cell types and closely resembled that described for cultures of sprouting endothelium. These alterations in secretory phenotype may reflect: 1) a true difference in cell type between capillary and other types of endothelium, 2) differences resulting from cell isolation and initial culture conditions, or 3) a correlation between growth regulation and protein synthesis.