Morphometric study of the mucous cells in albino rat zymogenic units

ABSTRACT

The present study was carried out to throw light on the morphometric and ultrastructural changes in the different mucous secreting cells in the rat zymogenic units during cellular migration along the zymogenic units. Twenty adult albino rats [200 -250 gm] were used. The animals were perfused through the left ventricle, under Ketamine hydrochloride anaesthesia [45 mg / kg], with lactated Ringer's solution followed by a mixture of 2.5% gluteraldehyde and 2% paraformaldehyde in 0.1 M cacodylate buffer [pH 7.4]. Fine fragments were taken from the fundus of stomach fixed in the same mixture, post fixed in osmium tetroxide, dehydrated in alcohols and propylene oxide, and embedded in Epon. Semithin sections were cut by a glass knife, stained by toluidine blue and used for morphological study and counting of pit and neck mucous cells. Ultrathin sections were cut also with glass knife, stained with uranyl acetate and lead citrate, examined by JEOL 100S E / M. The pit region was arbitrarily divided into low, mid, high pit as well as pit top segments. The neck was similarly divided into high and low segments. The number of cells in these different pit and neck segments was counted in longitudinal sections of twenty zymogenic units for each animal. The size of secretory granules, and mitochondria were measured in 6 micrographs from different units for each cell type. The data obtained from the pit segments were statistically analyzed for the test of significance as compared to the low pit values, those of low neck region obtained from the high neck ones, in the different pit regions as compared with the low pit segment. The low pit cells showed two rows of ectoplasmic secretory granules with dense cores while their cytoplasm contained supranuclear Golgi apparatus with prospectory vesicles at its trans-face, numerous mitochondria few rER cisternae and many free ribosomes. In the cell of the mid pit there were more raws of secrtory granules with diminution of the free ribosomes. In the high pit cells, the ectoplasm was full of many rows of secretory granules, while the free ribosomes were little in amount. A well developed Golgi apparatus with prosecretory vesicles at its trans face was also evident in these cells. The cells at the pit top had few ectoplasmic secretory granules, rounded pale mitochondria, few rER cisternae. The degenerating pit top cells were characterized by the appearance of several clear spaces in the cytoplasm, their nuclei became condensed and irregular while the ectoplasm housed few, ovoid secretory granules; few of which had dense cores. The remaining cytoplasm contained dilated rER cisternae and pale mitochondria. The completely degenerated pit top cells became separated from the adjacent ones by wide intercellular spaces, their dense cytoplasm contained ghosts of mitochondria, rER and scattered lysosomes. Statistically, there was a significant decrease in the number of cells, a significant increase in the size of secretory granules and a significant decrease in the size of mitochondria in all pit segment cells as compared with the low pit ones. The secretory granules of the high neck cells exhibited irregular cores while the cytoplasm showed long rER cisternae, scattered free ribosomes, Golgi stacks and mitochondria. In the low neck cells the granules possessed cores of variable electron density and the rER cisternae surrounded the nucleus. Statistically there was a significant increase in the number of cells in the low neck segment, as compared with the high neck ones. There was also a significant increase in the sizes of both secretary granules and mitochondria in the low neck cells as compared with those in high neck segment. At the border between neck and base, prezymognic cells containing rounded secretary granules with more electron dense material, were encountered. It could be concluded that the activity of pit cells increased as we go up to its high part and decreased at the pit top where they degenerated and became extruded into the gastric lumen. On the other hand, the neck cells became more active as they descended down to the base to be transformed into zymogenic cells