Metabolism of rat granular pneumocytes isolated in primary culture

Abstract

Granular pneumocytes (GP) were isolated by trypsinization of minced rat lungs followed by short-term primary culture. The yield from the lungs of 1 rat was approximately 3.5 .times. 106 GP, representing 25 .mu.g DNA and 0.5 mg protein. Depending on the method to remove cells from attachment of plastic, the purity was 82-92% GP, of which > 90% excluded erythrosin B. Resting O2 consumption (37.degree. C) of cells was 202 .+-. 29 (mean .+-. SE, n = 3) nmol .cntdot. h-1 .cntdot. (106 cells)-1 with a 2.5 times increase in the presence of an uncoupler of oxidative phosphorylation. ATP content of resting penumocytes was 41. .+-. 0.18 nmol .cntdot. (106 cells)-1 and was markedly depressed by the uncoupling agent. During incubation with [U-14C]glucose, production of metabolites in nmol .cntdot. h-1 .cntdot. (106 cells)-1 was lactate 58.0 .+-. 7.9, pyruvate 25.8 .+-. 3.2 and 14CO2 56.4 .+-. 2.1, and glucose utilization was 104 .+-. 38.5. Sonicated GP had higher activities of both lactate and succinate dehydrogenases compared with alveolar macrophages. Alkaline phosphatase activity was localized predominantly to GP; macrophages contained predominantly acid phosphatase. The intracellular water space for granular pneumocytes was 0.55 .+-. 0.05 ml .cntdot. (106 cells)-1 and was 71% greater for alveolar macrophage. The presence of active glycolytic and oxidative pathways and appropriate responses to metabolic inhibitors and substrates suggest the presence of intact cell membranes and the retention of metabolic control mechanisms in this isolated lung epithelial cell preparation.