Abstract
Purpose: Surfactant proteins exist in the digestive tract and may play an important role in the host defense. However, the expression of surfactant proteins in the premature digestive system remains unclear. The aim of this study was to investigate the expression of surfactant proteins in the intes-tines and pancreas of murine fetuses. Methods: Immunostaining for SP-A and SP-D was assessed in the small intestine and pancreas of ICR murine fetuses on days 15, 16, 17 and 18 of gestation (normal duration of pregnancy: 19 - 21 days). RT-PCR was performed to detect the expression of spa and spd mRNA in the small intestine and pancreas on day 16, 17 and 18 of gestation. Results: Immunoreactivity for SP-A and SP-D in the acinar cells of pancreas and intestinal mucosal surface were positive on day 16 of gestation onward. RT-PCR revealed that the expression of spa and spd mRNA was significant in the pancreas but weak in the small intestine. Conclusions: Our data revealed that surfactant proteins are present in the fetal intestines and pancreas and that a significant expression of spa and spd mRNA is detected in the fetal pancreas. Pancreas may be a possible organ involved in the synthesis and secretion of surfactant proteins into the intestinal lumen.
Highlights
Pulmonary surfactant is a mixture of lipids and proteins that contains four specific surfactant proteins named SP-A, SP-B, SP-C and SP-D
Immunohistochemical Analysis of SP-A and SP-D The lungs, pancreas and small intestines of the adult mice were examined with respective antibodies
Different from the reactivity observed in the pancreas, the mucosal surface of the fetal intestines was positively immunostained for both SP-A and SP-D starting on day 15 of gestation, the mucosal cells exhibited intracellular weak reactivity for both SP-A and SP-D on day 18 of gestation (Figures 5, 6)
Summary
Pulmonary surfactant is a mixture of lipids and proteins that contains four specific surfactant proteins named SP-A, SP-B, SP-C and SP-D. Recent studies have revealed that these surfactant proteins are involved in the host defense, immunomodulation and production of surfactant lipids [1] [2]. SP-A and SP-D are hydrophilic and belong to the collectin subgroup of C-type lectins, playing an important role in innate immunity [3]. It has been reported that surfactant proteins exist in the gastrointestinal mucosal surface [6]. Considering their surface activity and immunomodulatory effects in the lungs, surfactant proteins in the digestive tract may play an important role in the host defense, especially in neonates. The expression of surfactant proteins in the fetal digestive system has not yet been described
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