We examined the effect of dextran (molecular weight 71,000) in counteracting the surfactant inhibitory action of plasma albumin. The surface adsorption time of 0.5 mg/ml modified natural surfactant (MNS; porcine lung extract consisting of phospholipids and hydrophobic surfactant proteins) with 7.5 mg/ml albumin decreased from 681 to 143 s by addition of dextran at a concentration of 10 mg/ml (P < 0.01). The minimum surface tension of 2.0 mg/ml MNS with 30 mg/ml albumin decreased from over 21 mN/m to below 3 mN/m when dextran was added at a concentration of 10 mg/ml (P < 0.01). Surfactant-deficient newborn rabbits given 10 ml/kg of a liquid containing 2.0 mg/ml MNS with 30 mg/ml albumin had a mean tidal volume 13 ml/kg (P < 0.05). Although the underlying mechanism remains to be elucidated, we conclude that dextran restores the albumin-inhibited surface activity of MNS.

Impairment of surfactant is a factor involved in the development of acute lung injury caused by inhalation of fabric protector. Surfactant replacement may be therapeutic for such injuries.

In this acute lung injury model, the effects of replacement therapy with surfactant consisting of synthetic phospholipids, SP-B and SP-C, were the same as those observed with MNS. These results warrant development of surfactant substitutes based on natural SP-B and SP-C, and synthetic phospholipids.

From the exercise task, 17 out of 54 (38%) asthmatic children developed reproducible early and late response after bicycle ergometer exercise task. There was a significant correlation between the magnitude of their early and late reactions, emphasizing the direct relationship between these two phenomenon. Inhalation of 81mKr gas allowed us to detect uneven distribution images very clearly. By changing the inhalation speed, we were able to obtain two different types of pattern, namely, type A dominant upon fast gas inhalation which affected large airways, and type B dominant upon slow gas inhalation which affected the small airways. Through this inhalation technique, we were able to detect which part of the bronchus had been affected. EIA patients showed variation in the affected areas, some only showing influence to the large airways, while other only to the small airways. Key words EIA (exercise-induced asthma) EILA (exercise-induced late asthmatic response) 81mKr gas inhalation NCA (neutrophil chemotactic activity) asthma is hyper-reactivity of the bron-Address: Department of Allergy, National Children's Hospital, 3-35-3 1, Taishido, Setagaya-ku, Tokyo, Japan Telephone: 03-4 14-8 121 Vol. 25 No. 4 Dec.. 1983 380(52) Y. Iikura et al.

Surfactant protein (SP)-C is characterized by alpha-helix structure and palmitoyl groups attached to two cysteine residues. We examined the function of palmitoylation and dimerization in promotion of tidal volume in immature newborn rabbits. Reconstituted surfactants were made from a mixture of synthetic phospholipids and porcine SP-B (basic mixture) by adding various forms of SP-Cs: normal SP-C isolated from porcine lungs and monomeric or dimeric forms of SP-C. These latter two were isolated from patients with pulmonary alveolar proteinosis and were less palmitoylated. Animals were ventilated at an inspiratory pressure of 25 cmH2O. Median tidal volumes were <2 ml/kg in nontreated controls, 7.7 ml/kg in animals receiving the basic mixture without SP-C, and >18 ml/kg in animals treated with reconstituted surfactants containing 3% normal or 2% dimeric SP-C (P < 0.05 vs. basic mixture). The physiological effect of basic mixture was not improved by monomeric SP-C. We conclude that palmitoyl groups are important for the physiological effects of SP-C and that the dimeric form also improves physiological effects.