A stereological evaluation of secretin and gastric inhibitory peptide-containing mucosal cells of the perinatal small intestine of the pig

Abstract

Stereological methods were used to quantify secretin and gastric inhibitory peptide (GIP)-immunoreactivity (GIP-IR) in paraffin sections of the duodenum, jejunum and ileum of fetal and neonatal piglets. In addition, sections were processed for GLP-1-immunohistochemistry. The volume density of the tunica mucosa increased after birth, giving rise to a decreased volume density of the tela submucosa and tunica muscularis. Generally known region-specific morphological distinctions were reflected in differing volume densities of the various layers. The highest volume density of GIP-IR epithelial cells was observed in the jejunum of the neonate. In contrast, the volume density of secretin-IR epithelial cells was highest in the duodenum of both fetal and neonatal piglets. The volume occupied by GIP-IR and secretin-IR epithelial cells increased in the jejunum after birth. Additionally, ileal secretin-IR epithelial cells were more numerous in the neonatal piglet. In conclusion, the quantitative and qualitative presence of GIP-IR and secretin-IR epithelial cells agree with earlier reports of their presence and co-localization between GIP-IR and GLP-1-IR, in the pig small intestine. Furthermore, the differences suggest that age- and region-related functional demands are temporally and probably causally related with the morphological diversification of the intestine and its endocrine cells.

Fig. 1

GIP-IR epithelial cells (arrows) in the ileum of a 2-day-old neonatal piglet. One GIP-IR epithelial cell (arrowhead) clearly shows an apical process that reaches the lumen of the crypts. Scale bar, 50 µm.

Fig. 2

GIP-IR epithelial cell in the jejunum of a 2-day-old neonatal piglet. The arrow indicates a GIP-IR cell that is also immunoreactive for GLP-1 (see Fig. 3). Scale bar, 50 µm.

Fig. 3

GLP-1-IR epithelial cells (arrowhead) in the jejunum of a 2-day-old neonatal piglet. The arrow points to a GLP-1-IR cell that also is immunoreactive for GIP (see Fig. 2). Scale bar, 50 µm.

Fig. 4

Secretin-IR epithelial cells (arrow) in the duodenum of a 4-day-old neonatal piglet. Scale bar, 50 µm.

Fig. 5

Mean volume densities of tunica mucosa (dark grey bar), tela submucosa (white bar), tunica muscularis (light grey bar) and tela serosa (black bar) according to small intestinal region (A: duodenum descendens; B: duodenum ascendens; C: jejunum and D: ileum) and age.

Fig. 6

Volume density of GIP-IR epithelial cells according to small intestinal region (A: duodenum descendens; B: duodenum ascendens; C: jejunum; D: ileum) in fetal (white box) and neonatal (black box) piglets (mean and 68% confidence interval).

Fig. 7

Volume density of secretin-IR epithelial cells according to small intestinal region (A: duodenum descendens; B: duodenum ascendens; C: jejunum; D: ileum) in fetal (white box) and neonatal (black box) piglets (mean and 68% confidence interval).