In vivo protein secretion by lung. Evidence for active secretion and interspecies differences.
The present study is an attempt to determine (a) if the lung actively secretes protein into the surface-active fraction of lung lavage returns; (b) if there are interspecies differences in this secretory activity; and (c) if the amount of nonradioactive protein in the lavage surface-active fraction shows interspecies variation. I found that pilocarpine stimulates the release of radioactive protein into the lavage surface-active fraction of rabbits and that this pilocarpine effect is completely blocked by atropine. Inhibition of lung oxygen consumption by iodoacetate is associaged with a dose-dependent inhibition of the pilocarpine-induced secretion. Microtubules may be involved in this secretory process because colchicine inhibits the pilocarpine effect. Of the radioactive protein in the total surface-active fraction (tissue plus lavage returns), a greater percent appears in the lavage surface-active fraction at 2 and 4 h, after a pulsed injection [U-14C] leucine, in the mouse than in the rat, which in turn has a greater amount than the rabbit. There is also a difference in the amount of nonradioactive protein per square meter of alveolar surface area in the lavage surface-active fraction of different species: mouse greater than rabbit greater than cat greater than dog. The amount of nonradioactive protein per square meter of alveolar surface area in the lavage surface-active fraction is directly proportional to the species respiratory rate; the log of the nonradioactive protein in the lavage surface-active fraction is inversely proportional to the log of the species alveolar diameter. I conclude that the lung actively secretes protein into the lavage surface-active fraction, that this secretion is under neurohumoral regulation, and that respiratory rate and alveolar size may influence this secretory activity and the amount of protein in this surface-active fraction.
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002250:Carbon Radioisotopes; D003078:Colchicine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D007461:Iodoacetates / Q000494:pharmacology; D007930:Leucine / Q000032:analysis; D008168:Lung / Q000378:metabolism*; D008297:Male; D051379:Mice; D010101:Oxygen Consumption / Q000187:drug effects; D010862:Pilocarpine / Q000494:pharmacology; D014176:Protein Biosynthesis; D011663:Pulmonary Surfactants / Q000502:physiology*; D011817:Rabbits; D051381:Rats; D013045:Species Specificity; D007507:Therapeutic Irrigation
D002250:Carbon Radioisotopes; D007461:Iodoacetates; D011663:Pulmonary Surfactants; D010862:Pilocarpine; D001285:Atropine; D007930:Leucine; D003078:Colchicine