The surface-associated surfactant reservoir in the alveolar lining.
A small atmospheric bubble was introduced into a surfactant suspension in a captive bubble surfactometer. After film formation to the equilibrium surface tension at the bubble air-liquid interface, the bulk phase surfactant was depleted by replacing the chamber contents several times with a saline-CaCl2 solution. The remaining film adsorbed at the bubble surface was then compressed stepwise in quasi-static fashion to near zero minimum surface tension. This was followed by a series of quasi-static expansion steps to surface tensions slightly above equilibrium. The surface tension of films from lipid extract surfactants and phospholipid mixtures did not increase in a manner consistent with the presence of a single surface monolayer. After the initial, rapid rise in surface tension at each expansion step, a decrease in surface tension to a new value was observed. This decrease in surface tension is likely due to the adsorption of 'surplus' material from a 'surface-associated reservoir' into the surface active film. The presence of surplus non-monolayer surfactant material in situ at the alveolar surface was also demonstrated by electron microscopy. SP-A acted as a potent promoter for the movement of excess material (equivalent to 2-3 monolayers) at the interface into the surface active film. In contrast, inhibitory serum proteins prevented the formation of a surface-associated reservoir or the adsorption of excess material into a surface active film.
Schürch
S
S
Respiratory Research Group, Faculty of Medicine, University of Calgary, Canada.
Qanbar
R
R
Bachofen
H
H
Possmayer
F
F
D000327:Adsorption; D000818:Animals; D002122:Calcium Chloride; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects / Q000502:physiology; D008854:Microscopy, Electron / Q000379:methods; D011510:Proteolipids / Q000032:analysis / Q000502:physiology; D011650:Pulmonary Alveoli / Q000737:chemistry* / Q000502:physiology* / Q000648:ultrastructure; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000032:analysis* / Q000502:physiology; D011817:Rabbits; D012710:Serum Albumin, Bovine / Q000494:pharmacology; D013500:Surface Tension
D011510:Proteolipids; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; D012710:Serum Albumin, Bovine; D002122:Calcium Chloride