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.
Highlights
Gastric acid secretion is regulated by both the autonomic nervous system and hormones
The gastric juice pH of the adrenalectomized, hypergravity-exposed rats (3.00±0.15) was not significantly different from that of the adrenalectomized, nonexposed rats (2.94±0.16; P = 1.000; Figure 1C). These results indicate that adrenalectomy produced a significant increase in gastric juice volume and acidity, suggesting that the adrenal glands are required for hypergravity-induced gastric acid hyposecretion in rats
Effects of hypergravity exposure and adrenalectomy on gastric juice parameters First, we examined the influence of hypergravity exposure on gastric juice parameters
Summary
Gastric acid secretion is regulated by both the autonomic nervous system and hormones. The parasympathetic nervous system and gastrin stimulate the parietal cells to produce gastric acid, both directly acting on the parietal cells and indirectly through the stimulation of histamine secretion from the enterochromaffin-like cells [1]. The highly acidic environment in the stomach causes proteins from food to lose their characteristic folded structure. This exposes the peptide bonds of the proteins. The chief cells of the stomach secrete the enzyme for protein breakdown, inactive pepsinogen [2]. Gastric acid activates pepsinogen into pepsin, which helps digestion by breaking the bonds linking the amino acids in a process known as proteolysis. Many microorganisms have their growth inhibited by such an acidic environment, which is helpful for preventing infection [1,2,3]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
