Quantification of an apoprotein of pulmonary surfactant in normal and alloxan-induced diabetic rats by electroimmunoassay.

Abstract

We have quantitated a specific apoprotein of rat pulmonary surfactant using an electroimmunoassay and have examined its content in the lungs of alloxan-induced diabetic rats. Rat lung surfactant was purified and was used to raise antisera in rabbits. Antibodies against rat serum proteins were removed from the IgG fraction of the antiserum by means of affinity chromatography using rat serum-linked to Sepharose 4B. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of rat surfactant revealed the presence of one major protein, a molecular weight of about 16,000 dalton, and this protein was a non-serum protein and specific to the lung by immunological tests. It seems likely that the 16,000 dalton protein obtained in the present study is similar to the 11,000 dalton or to a fragment of the 34,000 dalton protein, reported by other investigators. Using the monospecific antiserum against this protein of rat surfactant, the apoprotein content of pulmonary surfactant in alloxan-induced diabetic rats was measured by means of rocket electroimmunoassay. The lungs of diabetic rats contained less of this apoprotein than the lungs of control rats. This finding suggests that diabetes mellitus may induce a disturbance of protein metabolism in the lungs, as well as of carbohydrates and phospholipids, which may cause pulmonary dysfunction in diabetic patients observed in our previous studies.