Ultrastructural localization of atrial natriuretic peptide-synthesizing cells in rat gastric mucosa and the correlation of atrial natriuretic peptide-synthesizing cells to microvessel density

Chunhui LI; Lihui PAN; Wenbin ZHANG; Shi YAN

ABSTRACT

BACKGROUND:

Previous studies have confirmed that atrial natriuretic peptide (ANP) exists in different regions of rat gastric mucosa in different densities, and ANP can inhibit the spontaneous contraction of gastric smooth muscles in rat, guinea pig and human.

OBJECTIVE:

To investigate the ultrastructural localization of ANP-synthesizing cells and the correlation between ANP-synthesizing cells and microvessel density in rat gastric mucosa.

DESIGN:

Single sampling study.

SETTING:

Affiliated Hospital of Chengde Medical College. MATERIALS Eighteen adult male Wistar rats of clean grade, weighing 300-350 g, were used in this study.

METHODS:

This study was conducted in the Laboratory of Chinese Materia Medica Immunology, Chengde Medical College from October 2004 to July 2007. The ultrastructural localization of ANP-synthesizing cells in rat gastric mucosa was performed by postembedding immunoelectron microscopy technique. The area density of ANP-synthesizing cell distribution was calculated by histochemical technique (saffron solution and toluidine solution staining included). Microvessels of rat gastric mucosa were revealed distinctively by tannic acid-ferric chloride staining method and scanning electron microscope technique.MAIN OUTCOME

MEASURES:

①The ultrastructural localization of ANP-synthesizing cells in rat gastric mucosa.②The distribution characteristics of gastric microvessels in different regions of rat gastric mucosa.③The distribution characteristics of ANP-synthesizing cells in rat gastric mucosa.④Correlation between ANP-synthesizing cell distribution and microvessel density.

RESULTS:

① Ultrastructural localization of ANP-synthesizing cells It was confirmed that ANP-cells were the enterochrochromaffin (EC) cells. ② Observation of microvessels The microvessels were stained successfully by tannic acid-ferric chloride and scanning electron microscope technology. Microvessels of gastric mucous were in wriggled way and cut in different cross-sections. They could be clearly observed in distinct three-dimensions. The microvessel density was the largest in the basal glands of rat gastric mucous. ③ Distribution of ANP-synthesizing cells It was identified that EC cell was only a chromaffin cell in the rat gastric mucosa. The chromaffin granules (brown granules) were localized in the cytoplasm of EC cells. Negative staining for chromaffin granules was detected in the submucosa and smooth muscle. EC cells had different distribution densities in different regions. The density order of EC cells was gastric cardiac region ＞ gastric pyloric region ＞ gastric fundic region in mucosal layer. ④ Correlation between ANP-synthesizing cells and microvessel density Correlation analysis showed that there was a positive correlation between ANP-synthesizing cells and microvessel density in the gastric cardiac region(r = 0.53, P ＜ 0.05, n=18), and there was a negative correlation between above-mentioned two indices in the gastric pyloric region(r = 0.38, P ＞ 0.05 , n=18)and in the gastric fundic region(r = -0.29, P ＞ 0.05, n=18).

CONCLUSION:

ANP-synthesizing cells are the EC cells of gastric mucosa. There is a positive correlation between ANP-synthesizing cells and microvessels in the rat gastric cardiac region, while there is a negative correlation between ANP-synthesizing cells and microvessels in the rat gastric pyloric region and in the gastric fundic region.