Abstract
Polycations are potent mediators of cellular secretion in a variety of cell systems through interaction with neuropeptide binding sites (e.g., substance P). We tested whether compound 48/80 or other polycations alter surfactant release from Type II cells, 3H-Choline was used to label phosphatidylcholine pools and release of 3H-phosphatidyl-choline (3H-PC) assessed in purified rat Type II cells. 48/80 and polymyxin B (PB) were potent inhibitors of terbutaline-stimulated and basal 3H-PC release IC50 was 1–2μ/ml for 48/80 and 5μg/ml for PB. Control release of 3H-PC was 1.17±3.17% and decreased to −0.23±0.09% in the presence of 48/80 (10μg/ml) or to 0.40±0.09% in presence of PB (5μg/ml, p<0.05 for both agents). Control release of 3H-PC from terbutaline-stimulated cells was 6.45±0.49% decreasing to 2.25±0.61% in the presence of 48/80 (10μg/ml, p<0.001). PB (5μg/ml), also inhibited terbutaline-stimulated 3H-PC release (control=3.32±0.47% and PB=1.67±0.33%, p<0.05). Neither polycation was cytotoxic as judged by lactate dehydrogenase release. This inhibition was readily reversed by washing cells after exposure to either agent. Larger polycations, polyarginine, polyornithine and polylysine had no significant effect on 3H-PC release at concentrations <5μg/ml and were cytotoxic at concentrations >5μg/ml. Inhibition of 3H-PC release by 48/80 and PB appears to be site specific since polylysine, polyarginine and polyornithine did not alter 3H-PC release. These data support existence of a counter-regulatory system mediating surfactant secretion from Type II cells, possibly mediated by neuropeptide binding sites. Supported by American Lung Association, NIH HL 28623 and HD 11725.
Article PDF
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Rice, W., Singleton, F. & Whitsett, J. 304 REGULATION OF SURFACTANT SECRETION FROM ISOLATED TYPE II CELLS BY LOW MOLECULAR WEIGHT POLYCATIONS. Pediatr Res 19, 161 (1985). https://doi.org/10.1203/00006450-198504000-00334
Issue Date:
DOI: https://doi.org/10.1203/00006450-198504000-00334