Immunohistochemical studies on the development of cells containing progastricsin (minor pepsinogen) in comparison to prochymosin and pepsinogen in bovine abomasal mucosa.

The localization of progastricsin was studied in cells of abomasal mucosa from cattle of different ages and feeding regimes and compared to the localization of prochymosin and pepsinogen in the same material by use of an immunofluorescence technique with specific rabbit antibodies. Immunoreactivity for progastricsin was first found in calves at the age of about 45 days in surface mucous cells in the pit of the fundic gland. In older calves and adults, mucous neck cells also produced progastricsin. In the pyloric mucosa, on the other hand, traces of progastricsin immunoreactivity were found in the lower base of the pyloric gland even in newborn calves. When the calves grew older, progastricsin-immunoreactive cells also developed in the pit and later in the neck of the pyloric gland; and the number of these cells in this region increased with age. The development of progastricsin-producing cells seemed to be influenced only by age and not by the feeding of milk to the calves. The ontogeny of progastricsin, prochymosin, and pepsinogen exhibited an interesting pattern in cattle, as they started to be produced at three different ages and gave three different patterns of development in the cells of abomasal mucosa. The number of cells producing prochymosin was closely correlated with milk-feeding, while the development of progastricsin was most related to the age of the calf. The most stable factor during the development of the cells in the abomasum was the number of cells producing pepsinogen.