Differential expressions of surfactant protein SP-A, SP-B, and SP-C mRNAs in rats with streptozotocin-induced diabetes demonstrated by in situ hybridization.

We have previously demonstrated by in situ hybridization and Northern blot analysis that alveolar type II cells and nonciliated bronchiolar epithelial (Clara) cells in lungs of rats with diabetes have decreased surfactant protein A (SP-A) but increased mRNA. In the present study, we have examined the mRNA expression and localization of two hydrophobic surfactant proteins, SP-B and SP-C, and have compared them with SP-A mRNA levels and cellular localization in streptozotocin-induced diabetic lungs. Localization and level of expression were analyzed by in situ hybridization using type-specific, surfactant cDNA probes. Diabetes was induced in adult rats by an intraperitoneal injection of 60 mg/kg streptozotocin. Ten weeks after injection, higher numbers of silver grains representing SP-A and SP-B mRNAs were observed in alveolar type II cells of diabetic lungs, compared with control lungs. Moreover, the number of silver grains representing SP-C mRNA decreased in alveolar type II cells from diabetic lungs compared with controls, and no silver grains for SP-C mRNA were present in bronchiolar epithelial cells from either control or diabetic groups. In contrast, in bronchiolar epithelial cells of diabetic lungs, the relative abundance of silver grains for SP-A mRNA increased approximately 2-fold above controls, while SP-B mRNA decreased slightly. Taken together, there is differential expression in the level of SP-A, SP-B, and SP-C mRNAs in both alveolar and bronchiolar epithelial cells from diabetic lungs when compared with control lungs.(ABSTRACT TRUNCATED AT 250 WORDS)