Localization of ANP-synthesizing cells in rat stomach

Abstract

Aim: To study the morphological positive expression of antrial natriuretic peptide (ANP)-synthesizing cells and ultrastructural localization and the relationship between ANP-synthesizing cells and microvessel density in the stomach of rats and to analyze the distribution of the three histologically distinct regions of ANP-synthesizing cells.

Methods: Using immunohistochemical techniques, we studied positive expression of ANP-synthesizing cells in rat stomach. A postembedding immunogold microscopy technique was used for ultrastructural localization of ANP-synthesizing cells. Microvessel density in the rat stomach was estimated using tannic acid-ferric chloride (TAFC) method staining. Distribution of ANP-synthesizing cells were studied in different regions of rat stomach histochemically.

Results: Positive expression of ANP-synthesizing cells were localized in the gastric mucosa of rats. Localization of ANP-synthesizing cells identified them to be enterochrochromaffin cells (EC) by using a postembedding immunogold electron microscopy technique. EC cells were in the basal third of the cardiac mucosa region. ANP-synthesizing cells existed in different regions of rat stomach and its density was largest in the gastric cardiac region, and the distribution order of ANP-synthesizing cells in density was cardiac region, pyloric region and fundic region in mucosa layer. We have also found a close relationship between ANP-synthesizing cells and microvessel density in gastric mucosa of rats using TAFC staining.

Conclusion: ANP-synthesizing cells are expressed in the gastric mucosa. EC synthesize ANP. There is a close relationship between ANP-synthesizing cells and microvessel density in gastric mucosa of rats. The distribution density of ANP-synthesizing cells is largest in the gastric cardiac region.

Figure 1

Different histological regions of rat stomach. R: Cardic region or cardia; F: Fundic region or fundus; A: Pyloric region or antrum.

Figure 2

A: As a positive control, atrial myocytes show intense positive cytoplasmic staining for ANP (IHC × 200); B: Positive staining for ANP is localized to cytoplasm of mucosal cells in cardiac glands (IHC × 200); C: Positive staining for ANP is localized to cytoplasm of mucosal cells in cardiac glands (IHC × 400); D: As a negative control, complete absence of staining is observed when normal rabbit serum is substituted for ANP (IHC × 400).

Figure 3

A: localization of immunogold labeled in the endocrine granule of the enterochromaffin cell (TEM × 20 000, bar = 200 nm); B: Negative control,complete absence of immunogold labeled in the endocrine granule of enterochromaffin cells when normal rabbit serum was substituted for anti-ANP antiserum (TEM × 20 000, Bar = 200 nm); C: Normal enterochromaffin cells in gastric mucosa (TEM × 15 000, Bar = 500 nm).

Figure 4

The distribution of ANP synthesizing cells in different regions of stomach in rats. Mean ± SD. ^aP < 0.05 vs fundic region.

Figure 5

A: Microvessels of gastric mucous were in wriggled way and cut into different cross-sections, it could be clearly observed in distinct three-dimensions (arrow) (TA-Fe × 400); B: Some branch arteries from the large vessels run into the basal glands of the gastric mucosa (arrow) (TA-Fe × 400); C: There is positive significant relationship between the positive rate (%) of ANP-synthesizing cells and microvessel density (%) in cardiac region mucosa of rats (r = 0.53, P < 0.05, n = 18).