Further observations concerning the effects of hypophysectomy on the gastric mucosa of the rat.

Hypophysectomy in rats markedly reduced the weight and surface area of the stomach as well as the volume (mass) of the gastric mucosa and the total parietal and total peptic cell populations. The parietal cell population was reduced by about 50%, and this effect was due entirely to the reduction that occurred in the total surface area of the stomach (50%); the average number of parietal cells per unit area, which reflects the number of parietal cells in the gastric glands, was not affected. The peptic cell population was reduced by about 90%, the factors responsible being a reduction in the average number of peptic cells per unit area (70%) as well as the reduction that occurred in the surface area of the stomach. The disproportionate effect of hypophysectomy on the cell populations was thus due to the reduction in the number of peptic cells per unit area; this effect implies that hypophysectomy had caused a reduction in the number of the peptic cells in the gastric glands.Whatever the mechanisms involved these results were due to a direct effect of pituitary deprivation on the stomach, since they could not be accounted for simply by the inhibition of somatic growth that follows hypophysectomy in rats. Thus the experiment included a group of sham hypophysectomized rats whose somatic growth was inhibited to the same extent as that of the hypophysectomized animals by deliberate underfeeding. While underfeeding reduced the surface area of the stomach (20%) and the total peptic cell population (25%), as well as exerting a marginal effect on the parietal cell population, these effects were much smaller in magnitude than those of hypophysectomy; moreover underfeeding did not affect the number of peptic cells in the gastric glands. The results confirm that the pituitary gland exerts a strong influence on the growth of the gastricmucosa.