Abstract
Jet fighter pilots experience high gravitational acceleration forces in the cephalocaudal direction (+Gz), causing severe stress. Stress affects different physiological functions of the gastrointestinal tract. Although the effects of exposure to hypergravity on cardiovascular and cerebral functions have been the subject of numerous studies, crucial information regarding potential pathophysiological alterations following hypergravity exposure in the gastrointestinal tract is lacking. We recently documented a significant decrease in gastric secretory activity in rats after acute exposure to hypergravity. In the present study, we investigated the effects of adrenalectomy on gastric acid secretion and plasma gastrin level in hypergravity-exposed rats. Male Sprague-Dawley rats were adrenalectomized and exposed to +10Gz three times for 3 min. Gastric juice and blood samples were collected, and the volume and total acidity of gastric juice and plasma level of gastrin were measured. Consistent with our previous data, acute exposure to +10Gz significantly altered the gastric juice parameters in the sham-operated rats. The volume (P < 0.001) and acidity (P < 0.001) of gastric juice in the hypergravity-exposed rats were significantly lower than those in the nonexposed rats. In contrast, in adrenalectomized rats, the differences in the gastric juice volume (P = 0.712) and acidity (P = 0.279) were not statistically significant between the hypergravity-exposed and nonexposed rats. We demonstrated that adrenalectomy abolished hypergravity-induced gastric acid hyposecretion, but did not influence gastrin release. These findings suggest that the adrenal glands are required for hypergravity-induced gastric acid hyposecretion.