Expression of pulmonary surfactant protein D in rat gastric mucosa.

Gastric mucosa is protected from an acidic lumenal environment by an extracellular layer composed in part of phospholipids that are similar in composition to the phospholipids of lung surfactant. The function and metabolic processing of lung surfactant is regulated, in part, by surfactant specific proteins. We speculated that the gastric extracellular acid barrier might be regulated by such proteins. We demonstrate by RNA blot analysis, RT-PCR, and immunostaining and protein blot the synthesis of surfactant protein D (SP-D) in mucus-secreting cells of the gastric mucosa. SP-D protein and mRNA were not detected in the duodenum and the remainder of the gastrointestinal tract. We speculate that SP-D may participate in the regulation of secretion or assembly of the gastric acid barrier. Alternatively, SP-D may participate in gastric mucosal host defense.