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The present paper describes mucous cells in the forestomach glandular region which immunoreacted to antibovine pepsinogen serum in adult and young bactrian camels, Camelus bactrianus (female, 25 years old; female, 6 months old; from Hilar Inner Mongolia, People's Republic of China, in August 1988). These immunoreactive cells in forestomach glandular regions also reacted to Alcian blue (pH 1.0) and/or periodic acid-Schiff. Cross-reactivity of antibovine pepsinogen serum against extracts from the forestomach glandular region was analyzed by Western blotting, supporting that this serum could detect pepsin and/or pepsinogen in the bactrian camel. It was suggested that mucous cells in forestomach glandular regions produce pepsinogen molecules.

The presence of gastricsin in bovine abomasal juice has been reported previously, but its exact site of origin has not yet been established. Specific polyclonal antibodies were used in the peroxidase-antiperoxidase method or the protein A/gold technique to label cells producing progastricsin. This immunocytolocalization was correlated with that of pepsinogen and prochymosin using specific polyclonal antibodies against those zymogens. The present study clearly established that progastricsin was located exclusively in chief, mucous neck, transitional mucous neck/chief, foveolar epithelial and surface epithelial cells of the calf fundic mucosa. Furthermore, progastricsin was found to be colocalized with pepsinogen and prochymosin in the same secretory granules of these cells. Progastricsin was not observed in parietal, gastric endocrine and undifferentiated neck cells.

The electron immunocytochemical co-localization of prochymosin and pepsinogen in chief cells, mucous neck cells and transitional mucous neck/chief cells of calf fundic glands was studied using specific antisera for prochymosin and pepsinogen with a protein A-gold method. Prochymosin and pepsinogen immunoreactivities were detected in the same secretory granules of the chief, mucous neck and transitional cells, simultaneously using small and large colloidal gold particles. In chief cells, both immunoreactivities were distributed uniformly over the same zymogen granules showing a round, large, homogeneous and electron-dense appearance. In mucous neck cells, both immunoreactivities were found exclusively on the same electron-dense core located eccentrically in the mucous granule showing light or moderate electron density. In transitional mucous neck/chief cells, electron-dense cores became larger in size and some granules were occupied by the electron-dense core without a halo between the core and the limiting membrane. Both immunoreactivities were found uniformly over the electron-dense core. The granules having no halo in the transitional cells could not be distinguished from the typical zymogen granules in the chief cells.

Fundic mucosal extracts of the cat were examined by chromatography using DEAE-cellulose at pH 5.3. The peaks of proteolytic activity located by this method were shown to be heterogeneous on electrophoresis. By electrophoresis of individual homogenous chromatographic fractions 9 separate zones of proteolytic activity were detected. One zone did not migrate from the origin and is possibly a non-pepsinogen gastric protease. Simultaneous electrophoresis of pepsinogens and pepsins indicated that each pepsinogen gave rise to one pepsin. One zymogen gives rise to a pepsin active with the synthetic substrate acetyl-L-phenylalanyl-L-diiodotyrosine (APDT).

The presence of group I (Pg I) and group II (Pg II) pepsinogens was determined in 59 samples of human amniotic fluid between 11 and 40 weeks of gestation. Pg I was present in all of the samples, while Pg II was present only in samples of gestational age 32 weeks or older. No differential pattern of the fractions was present, although the first fraction of Pg I was not present in any of the samples. The sequential appearance of Pg I and Pg II suggests their fetal origin and that the synthesis of Pg I by fetal gastric mucosa may precede that of Pg II, thus serving as a potential marker of fetal maturity.

Pepsinogen I is normally produced by the chief and mucus neck cells of the fundic glands, while pepsinogen II is produced by these cells and by the cardiac and pyloric glands. In this study we used antisera specific for human pepsinogen I and II to identify these antigens in tumor tissue from 64 patients with gastric carcinoma. In addition, we examined the relationship between tumor positivity and preoperative serum levels of pepsinogens I and II. Histologically, 44 of the 64 cancers were of the intestinal type (gland forming) and 20 were of the diffuse type. Of the intestinal type tumors, 16 (36.4%) contained pepsinogen II, while only 2 (4.5%) contained pepsinogen I; one tumor contained both antigens. Pepsinogen II-positive cells were found in undifferentiated and in moderately well-differentiated intestinal type tumors, but not in intestinalized gastric mucosa or in tumors arising from intestinalized glands. This suggests that tumors containing PG II arise from antral gland mucosa even when most of the antrum has undergone intestinal metaplasia. None of the 20 diffuse tumors was positive for pepsinogen I and only 3 (15%) were positive for pepsinogen II. Serum pepsinogen II levels were available in 35 patients. The mean (+/- SE) level in 6 patients with pepsinogen II-positive tumors was 29.1 +/- 3.3 micrograms/l. This was higher than the mean level of 16.0 +/- 2.1 micrograms/l in the 29 patients with pepsinogen II-negative tumors (p = 0.011). Serum pepsinogen I was elevated to 152 micrograms/l in 1 of 2 patients with a pepsinogen I-positive tumor. The results suggest that tumor pepsinogen I and II enter the circulation and contribute to their respective serum levels.