THE ENDOCRINE SYSTEM AND THE STOMACH

Gastric mucosal damage induced by lateral hypothalamic lesions in female rats: influence of age and ovariectomy

Male rats given lateral hypothalamic (LH) lesions exhibit an acute increase in gastric acid secretion and develop erosions of the glandular portion of the stomach within 24 h. Since this process has been examined predominantly in male rats, the present experiments were devised to study the effects of LH lesions on the gastric mucosa of female rats. In Experiment 1, 1-year-old Sprague-Dawley female rats given LH lesions exhibited erosions in the rumenal portion of the stomach, a pattern unlike that found in both young and old male rats. Although the glandular mucosa lacked evidence of gross defects, the mucosa appeared blanched and covered with a mucus-like secretion. Experiment 2 demonstrated that, like male rats, LH lesions produced gastric hypersecretion in 1-year-old females. The results of the first two experiments indicate that the dissimilar patterns of gastric mucosal injury between males and older females cannot be accounted for on the basis of differences in gastric acid secretion. Experiment 3 demonstrated that, unlike older females but like males, 4-month-old female rats given LH lesions developed gastric erosions in the glandular mucosa only. Additionally, ovariectomy had no significant effect in altering the extent of gastric pathology. Taken together, these results suggests that (1) age and gender are important variables in neurogenic gastric mucosal injury, (2) differences in the type of gastric ulceration cannot be accounted for by differences in acid secretion, (3) ovarian hormones do not appear to play a significant role in gastric ulceration following brain damage.

Growth hormone increases the mass, the collagenous proteins, and the strength of rat colon

The effect of growth hormone treatment on the left colon was investigated in 4-month-old Wistar rats. The animals were injected with saline (controls) or biosynthetic human growth hormone (b-hGH) in doses of 1.0 and 5.0 mg b-hGH/kg/day for 30 days. The total body weight of the rats injected with 1.0 mg b-hGH/kg/day did not differ from that of the control group, whereas the body weight of the rats injected with 5.0 mg b-hGH/kg/day was increased by 37% compared with the control group. The colonic dry weight per unit length was increased by 57% and 46% by 1.0 mg and 5.0 mg b-hGH/kg/day, respectively. The defatted dry weight was increased by 52% and 44%, respectively. The hydroxyproline content per unit length was increased by 31% and 23%, respectively. Furthermore, the biomechanical strength was increased by the b-hGH injections. No difference between the two b-hGH doses was found in any of the data.

Feeding the premature and compromised infant: gastrointestinal considerations

We have presented the current concepts of gastrointestinal ontogeny--the various factors governing the ontogeny of the gastrointestinal tract and the interaction and intricate relationship between different determinants. It is only through a better understanding of the development of the gut and the various factors affecting it that pediatric gastroenterologists are able to design nutritional support strategies for managing very young and compromised neonates.

Cell kinetics of rat gastrointestinal mucosa. Autoradiographic study after treatment with 15(R)15-methyl-prostaglandin E2

Forty Sprague Dawley rats (120 g) were divided in groups of five rats each, and 2 mg , kg-1 15(R)15-methyl-prostaglandin E2 or vehicle was administered orally, twice daily for 5 days. On the 6th day, 1 mCi . kg-1 methyl-3H-thymidine was given intraperitoneally to all rats. Groups of rats were killed at 45 min and 24 h, 72, and 120 h after the labelling. Treatments were continued until death. Samples were taken from the corpus, antrum, and jejunum and processed for autoradiography. Microscopic evaluation of the proliferative and functional compartments included cell counts and determination of the labelling index (LI) and mitotic index (MI). Prostaglandin treatment increased the number of cells in the jejunal and gastric epithelia. The DNA synthesis, evaluated from the LI and 45 min after thymidine injection, was unaffected by treatment. The clearance of label from jejunal crypts and villi was significantly slower in the prostaglandin groups. Similar observations were made in the proliferative zone of the corporal and antral epithelia. The MI was unchanged or reduced by prostaglandin treatment, the reduction being significant after 8 to 10 days' treatment. It is suggested that the trophic action of prostaglandin E2 is produced by reduction of epithelial cell losses, thereby prolonging the cell survival time. The reduced MI may be secondary to negative feedback from the hyperplastic epithelium. Trophic actions are produced by short-term treatments.

Cortisol excretion into gastric juice. Studies in health, in digestive ulcer disease, and in surgery stress

Gastric juice cortisol concentrations in 36 healthy subjects in the basal state was 10.5 +/- 2.1 ng/ml. After stimulation with pentagastrin it was 11.5 +/- 3.2 ng/ml. There were no differences related to age or sex. Cortisol outputs were 25.9 +/- 12.1 ng/min in the basal state and 35.9 +/- 13.2 during pentagastrin stimulation. After stimulation with ACTH in 6 subjects gastric juice cortisol concentration increased 5.4 times while gastric cortisol output increased 19-fold. The plasma cortisol rose by a factor of 2.3 while the plasma free cortisol rose by a factor of 2.6. Gastric juice cortisol concentration increases correlated with concentrations of free and total plasma cortisol in plasma. When plasma levels of cortisol or dexamethasone were raised by intravenous infusions, the concentration in gastric juice depended on the free corticoid concentration in plasma. Gastric juice cortisol concentrations in 38 patients with gastric, duodenal, or combined gastric and duodenal ulcers were the same as in normal subjects. In 6 patients studied up to 6 days following abdominal surgery, both plasma and gastric cortisol concentrations were elevated but the increase in gastric juice cortisol was proportionally greater. This was not due to vagal stimulation, as shown by the failure of gastric juice cortisol concentrations to rise similarly during insulin hypoglycemia. Postsurgical increases in gastric juice cortisol may reflect the loss of protein-bound cortisol into the gastrointestinal tract as a result of injury to the gastric mucosa.

Effects of a combined oestrogen-progestin preparation on gastric acid and pepsin secretion, serum gastrin concentration and biliary secretion of bile acids, phospholipids, and cholesterol in the cat

1 Daily ethinyloestradiol (50 mug) and norethisterone acetate (1 mg) treatment (Minovlar) was investigated on gastric acid and pepsin secretion, and fasting serum gastrin concentration in six conscious female cats prepared with chronic gastric fistulae. The effect on biliary secretion of bile acids, phospholipids, and cholesterol was investigated in three conscious female cats prepared with chronic gastric and intestinal fistulae, and cholecystectomy.2 Treatment for 49 days did not alter the gastric acid or pepsin response to either intravenous pentagastrin infusions or a food stimulus. The fasting serum gastrin concentration remained unaltered throughout the study.3 Treatment for 18 days did not alter the percentage concentration of cholesterol in the bile, but reduced the percentage concentration of phospholipid. This was mirrored by a rise in the percentage concentration of bile acids in the bile. These trends were quickly reversed on cessation of treatment.4 There was no sign of cholestasis associated with the treatment. Intestinal flow remained constant throughout the study, there was no lithocholic acid or other abnormal bile acids detectable in any samples, and there was no change in serum aspartate aminotransferase concentration.5 The results suggest that in female cats, treatment with a combined oestrogen-progestin preparation does not exert any beneficial effects on the aetiology of peptic ulceration through the reduction of acid or pepsin secretion, or the lowering of serum gastrin concentration. The preparation shows a tendency to produce more lithogenic bile, and this may partly explain the greater incidence of gall stones in women on the contraceptive pill.

Characteristics and tachyphylaxis of gastrin-stimulated gastric acid secretion in the cat

1. The characteristics of gastrin-stimulated gastric acid secretion were investigated in conscious cats fitted with chronic cannulated gastric fistulae, with particular reference to tachyphylaxis. 2. There is a significant postive correlation between the peak acid secretion in response to pentagastrin 8 microgram kg-1 hr-1 and body weight. Male cats secret significantly greater amounts of acid in response to pentagastrin than females. The difference is lessened, but not eliminated, by expressing the acid out put in terms of body weight. 3. Pentagastrin stimulates a dose-dependent increase in acid secretion in the range 0.5-32 microgram kg-1 hr-1 when the response to each dose is assayed on separate occasions. Pentagastrin 64 microgram kg-1 hr-1 does not produce a further increase in acid secretion. The acid response to pentagastrin 1-16 microgram kg-1 hr-1 assayed on a single occasion by a continuous infusion method shows a dose-response relationship up to 8 microgram kg-1 hr-1 when it reaches a plateau of secretion. There is no difference between the two methods of assaying the gastric acid stimulating activity using doses of pentagastrin up to 8 microgram kg-1 hr-1. 4 The acid secretion in response to pentagastrin 8 microgram kg-1 hr-1 reaches a maximum after 45 min of stimulation and thereafter shows tachyphylaxis. Over a period of 5 hr there are at least two phases of tachyphylaxis distinguishable. During the period 0.75--2.5 hr of stimulation there is a fast phase of tachyphylaxis (-32.0 muequivH+kg-1 15 min-1). This is followed by a slow phase of tachyphylaxis (-9.4 muequivH+kg-1 15 min-1) up to 5 hr of stimulation. 5. The absolute rate of the fast phase of tachyphylaxis of acid secretion (muequivH+kg-1 15 min-1) increases with increasing doses of pentagastrin, but rates of tachyphylaxis are similar when expressed as a percentage of the peak acid response to the particular dose of pentagastrin (5.1--7.8% 15 min-1). Synthetic human gastrin-17, the synthetic C-terminal decapeptide of human gastrin and the C-terminal tetrapeptide of gastrin have comparable rates of tachyphylaxis. The possible receptor models for the tachyphylaxis of gastrin-stimulated acid secretion are discussed.

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.

Lean body mass, gastric acid, and peptic ulcer

Peak acid outputs in normal subjects and patients with duodenal and gastric ulcer were significantly (and similarly) correlated with body weight and calculated lean body mass. Expression of measurements of peak acid output as a function of body weight or lean body mass lessened but did not abolish the significance of the situation that men with no dyspepsia or gastric ulcer secreted more acid than women; the significant sex difference in duodenal ulcer was, however, abolished. Data for peak acid output have been tabulated, not only as m-equiv/hr but also as mu-equiv/kg body weight/hr and mu-equiv/kg lean body mass/hr. On the basis of the present data no change is suggested in the current expression of peak acid output as m-equiv/hr since expression of acid output as a function of body weight or lean body mass improves neither the variability nor the diagnostic discrimination of measurement of peak acid output.

Gastric secretion during pregnancy and lactation in the rat

1. Gastric acid secretion has been studied in the rat before, during and after pregnancy using different types of stomach preparation. During the same periods the histamine-forming capacity (HFC) has been determined in gastric mucosa and mammary gland.2. In rats with a whole stomach fistula interdigestive acid secretion is increased during pregnancy and lactation.3. In rats with a denervated chronic pouch secretory response to stimulation with gastrin and histamine is augmented during pregnancy and lactation.4. The histamine forming capacity (HFC) of the gastric mucosa is increased 2-3 times during the last days of pregnancy and also during lactation.5. The HFC of the mammary gland is increased 2-3 times during lactation as compared with the fully developed gland in pregnancy.