Dependence of surfactant function on extracellular pH: mechanisms and modifications.
We investigated alterations in pH on the surface properties of natural lung surfactant and the calf lung surfactant extract (CLSE), suspended in 10 mM N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid, using a pulsating bubble surfactometer. Increasing the pH value of the medium to > 7.4 decreased the ability of CLSE, but not of natural lung surfactant mixtures (2 mg phospholipid/ml), to achieve a low minimum surface tension during dynamic compression and enhanced their sensitivity to albumin inactivation. These detrimental effects on surface tension were reversed by addition of surfactant protein A (SP-A; 3% by weight) or by increasing the lipid concentration to 4 mg/ml. SP-A-induced lipid aggregation at pH 10 was not different than at pH 7.4. Alkalinization impaired the ability of CLSE to restore normal lung mechanics in excised surfactant-deficient rats lungs. These results indicate that cooperation between SP-A and the hydrophobic surfactant proteins has an important role in achieving low minimum surface tension at pH > or = 7.6.
Haddad
I Y
IY
Department of Pediatrics, University of Alabama at Birmingham 35294.
Holm
B A
BA
Hlavaty
L
L
Matalon
S
S
D000818:Animals; D004285:Dogs; D005110:Extracellular Space / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D050356:Lipid Metabolism; D011510:Proteolipids / Q000494:pharmacology; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000494:pharmacology / Q000502:physiology*; D012710:Serum Albumin, Bovine / Q000494:pharmacology
D011510:Proteolipids; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; D012710:Serum Albumin, Bovine