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 hypergravityexposed 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.
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The views and opinions expressed in this article are those of the authors and do not reflect the official policy or position of the Republic of Korea Air Force. The authors would like to thank Drs. Choong Sik Oh and Hye Sik Yun (Republic of Korea Air Force Aerospace Medical Center, Cheongju, Chungcheongbuk-do, Republic of Korea) for their technical assistance in conducting preliminary animal experiments. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2016R1D1A1B03935584) and by a faculty research grant of Yonsei University College of Medicine for 2016 (6-2016-0130).
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