An electron microscopic study of the acid mucosubstance lining the alveoli of hamster lung

Ultrahistochemical Study of Mucopolysaccharide at the Surface of the Alveolar Epithelium in a Rat Lung

“…The covering layer of acid mucopolysaccharide on the type II cell is thicker than that of the type I cell, namely 20-25 nm thick on the type II cell and 15-20 nm thick on the type I cell, in agreement with previous results (1,29,32). In addition, it has been demonstrated that the colloidal iron-reactivity of acid mucopolysaccharide of the type II cells is not completely abolished by either neuraminidase digestion (24) or methylation (22).…”

“…Colloidal iron-positive material was observed in a thin layer, 15-25 nm in thickness, closely attached to the luminal surface of the alveolar epithelium. The superficial layer, the hypophase, and the tubular-myelin figures, however, lacked the colloidal iron reactivity.Ruthenium red-positive material was observed on the luminal surface of the alveolar epithelium as well as in the hypophase.In the ultrathin sections stained with PTA (pH 0.4 and 1.5), the microvillous surface of the type II cell was densely stained, whereas the luminal surface of the type I cell was not discernible.The results suggest that acid mucopolysaccharide is not involved in the surfactant lining, but may be in existence as a surface coat on the alveolar epithelium; the surface coat on the type II cell differs chemically from that on the type I cell.Since Macklin (28) first described the presence of a lining layer on the alveolar surface, a number of histochemical and ultrahistochemical studies indicated that the lining layer consisted of neutral lipids (12, 23, 31), phospholipids (1, 6, 11, 12), proteins (20, 34) and mucopolysaccharides having affinities for colloidal iron (3,16,17,24,28,29), periodic acid-Schiff (3, 6, 9, 27), alcian blue (27), low iron diamine (27), ruthenium red (1,7,17,29, 33), chromic phosphotungstic acid (PTA) (1), concanavalin A (41) and high iron diamine (19). However, no relationship of these components to the surfactant lining was apparent, since in those experiments most of the surfactant lining was removed during the fixation procedure.…”

“…Since Macklin (28) first described the presence of a lining layer on the alveolar surface, a number of histochemical and ultrahistochemical studies indicated that the lining layer consisted of neutral lipids (12, 23, 31), phospholipids (1, 6, 11, 12), proteins (20, 34) and mucopolysaccharides having affinities for colloidal iron (3,16,17,24,28,29), periodic acid-Schiff (3, 6, 9, 27), alcian blue (27), low iron diamine (27), ruthenium red (1,7,17,29, 33), chromic phosphotungstic acid (PTA) (1), concanavalin A (41) and high iron diamine (19). However, no relationship of these components to the surfactant lining was apparent, since in those experiments most of the surfactant lining was removed during the fixation procedure.…”

'De‐watering' capabilities of surfactants in human amniotic fluid.

“…Hence there would seem to be many examples where direct adsorption of phospholipids similar in composition to lung surfactant can induce an appreciably hydrophobic surface, but this does not necessarily mean that it will do so at the pulmonary epithelial surface. However, it has been shown by Meban (1972) and Roth (1975) that there are acidic mucopolysaccharides incorporated into the alveolar wall or tightly bound to it, and these would provide the sites desirable for strong adsorption of surfactant. At the air-aqueous interface, Shah & Schulman (1965) have shown how cations, and especially calcium ions, can cause tighter bonding between adjacent orientated surfactant molecules (presumably via the phosphate ions) to produce a more condensed monolayer.…”

“…A, the concept of the hydrophobic alveolar wall with direct adsorption of surfactant and no intervening aqueous layer (Hills, 1982). Note the desirable configuration of the zwitterions in most components oflung surfactant, which provides a net force of attraction between the dipole of the hydrophilic moiety and the negative charges of the acid mucopolysaccharides comprising the exterior surface of the alveolar membrane as demonstrated by Meban (1972) and Roth (1975). This force of attachment is increased if Ca2+ or other cations neutralize the phosphate ions in the adsorbed monolayer in the same way as postulated at the air-aqueous interface by Shah & Schulman (1965).…”