Effect of hypophysectomy on the gastric mucosa of the rat

The contrasting influence of chronic nicotine intake on gastrin and gastric acid secretion

The effects of chronic nicotine treatment on gastric acid secretion stimulated by subcutaneous injection of pentagastrin, as well as on serum gastrin levels and the stomach parietal cell population, were examined. Rats drank a solution of nicotine 25 micrograms/mL tap water for periods of 10, 30 or 45 days. Pentagastrin increased the gastric secretory volume and acid output in pylorus-ligated control animals that drank tap water. Animals given nicotine in their drinking water for 10, 30 or 45 days showed increased basal gastric secretion and acid output. Pentagastrin produced maximum stimulatory effects at lower dose levels of 50 micrograms/kg in the 10-day treatment group and 25 micrograms/kg in the 30- or 45-day treatment groups; however, the maximum responses to pentagastrin in all nicotine-treated batches were comparable to those of their corresponding controls. Serum gastrin levels remained unchanged from the 10th day of nicotine treatment, whereas the levels in the control animals continued to rise with age. Nicotine 25 micrograms/mL drinking water given for 10, 30 or 45 days caused no significant changes in the parietal cell population, mucosal surface area or mucosal thickness. These findings are consistent with the idea that chronic nicotine administration, for at least 10 days, will lead to increased muscarinic receptor sensitivity; basal acid secretion is consequently elevated, and this in turn may depress gastrin secretion.

Brain ACTH prevents stress gastric lesions in rats

This study evaluated the effect of ACTH and several ACTH fragments on the development of gastric glandular lesions induced by cold-restraint stress in rats. Intracerebroventricular administration of ACTH1-39 dose-dependently (0.1-10 micrograms) inhibited stress gastric lesion formation. Studies with smaller molecular weight forms of ACTH (in a dose equimolar to 10 micrograms of ACTH1-39) revealed that ACTH1-13 and ACTH1-10 were also protective. The ACTH fragments ACTH5-10, ACTH34-39 and ACTH1-17 were without effect. Immunoneutralization of endogenous brain ACTH1-39 significantly increased stress gastric lesion severity. Antisera raised against synthetic somatostatin, gonadotropin-releasing hormone, and L-enkephalin were ineffective. These results with ACTH coupled with our previous demonstration of a protective effect of beta-endorphin suggest that specific brain pro-opiomelanocortin gene products modulate gastric mucosal integrity in response to stress.

Oral E2 prostaglandins affect endocrine cell populations in the gastric antrum of the rat

The aim of the present study was to investigate antral endocrine cell populations and tissue and circulating hormone levels following a 4-week oral regimen with prostaglandin E2 (25, 250 and 5000 micrograms/kg-1 b.i.d.) or a stable methyl analogue (5 and 50 micrograms kg-1 b.i.d.). Epithelial hyperplasia of the gastric antrum was observed with the highest dose of prostaglandin E2 and both doses of the analogue, as evaluated by stereological methods and conventional cell count. The treatments significantly affected the endocrine cell population. Somatostatin-immunoreactive cells were increased in proportion to the increased epithelial cellularity and plasma levels of somatostatin were increased in parallel. The tissue content of somatostatin-like immunoreactivity differed according to the extraction procedure used, and was significantly higher than controls in specimens extracted in neutral water. In the neutral extracts an immunoreactive somatostatin of unidentified molecular structure dominated quantitatively over somatostatin 14 and 28, which were the major components in acetic acid extracts. The serotonin-immunoreactive cell population was also significantly increased by natural prostaglandin E2 and the analogue but the gastrin cell population was not significantly affected by treatments. Accordingly, no significant changes were observed in tissue or plasma gastrin levels. It is concluded that the epithelial hyperplasia of the antral epithelia produced by E2 prostaglandins is associated with selective changes of endocrine cell populations. The changes were proportional to the increases of epithelial cellularity and required quantitative determination of the total antral volume to be detected.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of vagotomy on the distribution of sulphomucin-containing cells in the rat pyloric antrum

The present histological investigation showed that bilateral truncal vagotomy (with accompanying pyloroplasty) reduced the sulphomucin-containing cell population of the pyloric antral mucosa of the rat stomach. Although this did not reach statistical significance (95% confidence limits), study of the absolute distribution of the sulphomucin-containing cells showed that significantly fewer of these cells were situated in the basal third of the mucosa as a result of the operation. A study of the percentage distribution revealed that a much higher percentage of sulphomucin-containing cells was present in the middle third of the mucosa in vagotomized rats than in the corresponding regions of the control stomachs. Thus, vagotomy and pyloroplasty had effected a redistribution of the sulphomucin-containing cells in the pyloric antrum. The possible explanation and significance of this finding are discussed.

Cell differentiation in human gastric gland as revealed by nuclear binding of tritiated actinomycin

The nuclear binding of H3 actinomycin, which is closely linked to the differentiation phenomenon, was studied in human normal gastric mucosa. Actinomycin binding decreases in cells which differentiate and becomes very low in fully differentiated cells. In the gastric pits, there is a decreasing gradient of labelling from the deeper stem cells to the well-differentiated superficial cells. This indicates that migration and renewal of the surface epithelium occurs following a 'pipe-line' system. All the undifferentiated stem cells are labelled. Where the parietal cells are concerned all degrees of labelling are observed at various levels with a decreasing proportion of labelling from the surface to the bottom of the gland. With mucous cells and chief cells in the upper part of the gland a great number of poorly labelled mucous neck cells is observed. In the middle and lower part of the gland there is a new growth of heavily labelled cells. This means that in the normal human stomach chief cells probably do not originate from mucous cells.

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.

Hyperplasia of the gastric mucosa during pregnancy and lactation in the rat

1. The growth of the gastric mucosa during pregnancy and afterwards has been studied by comparing the stomachs of rats, killed at weekly intervals after impregnation, with the stomachs of virgin rats of the same age and starting weight. The rate of growth of the gastric mucosa in both groups was determined from the changes observed in the weight of the whole stomach, the weight and surface area of the fundus, the volume (mass) of the fundic mucosa and the total parietal and total peptic cell populations.2. Hyperplasia of the gastric mucosa occurred during pregnancy and lactation, the effect being characterized by increases in the surface area and volume (mass) of the gastric mucosa, and in the total parietal and total peptic cell populations.3. The data suggest that the effect developed shortly after conception. Hyperplasia of the gastric mucosa continued throughout pregnancy and reached maximal values after the second week of lactation and waned thereafter; the maximal changes obtained for individual observations such as surface area and the total parietal and total peptic cell populations represented increases of the order of 40% above corresponding control values.4. From the observations that were made on food intake it seemed unlikely that the hyperplasia of the gastric mucosa was due to hyperphagia. It also seemed unlikely that the effect could be accounted for by the increase that occurred in body weight during pregnancy.

The effect of hypophysectomy on the immune response

Twenty-one-day-old rats were hypophysectomized or sham-operated and challenged with sheep red blood cells 5 or 21 days after operation. Although the sizes of the bodies and lymphoid organs were greatly decreased in the hypophysectomized animals no significant difference was found in the numbers of plaque forming cells or serum antibody titres against the sheep red blood cells. The hypophysectomized rats showed a cell depletion in the perifollicular zone of the spleen follicles, but no obvious histological changes in the thymus.

It is concluded that pituitary hormones are not directly necessary for the formation of humoral antibodies.