Exposure to chronic noise and fractionated X-ray radiation elicits biochemical changes and disrupts body weight gain in rat

Abstract

The aim was to assess the developmental and biochemical effects resulting from separate and combined exposures to radiation and noise in adult male Sprague-Dawley rats. For 21 days, animals were exposed daily (1) to whole-body 121 kVp X-ray exposure (cumulative dose=5 Gy), (2) to random intermittent noise band-limited between 0.4 and 20 kHz; 2 h day(-1) 86 decibels (dB) and (3) to combined exposures. Control animals were housed under ambient noise conditions 55 dB A-weighted (dBA) and sham-exposed to X-rays. Body weight gain was significantly reduced in animals exposed to either X-rays or noise, and the loss was more pronounced in animals exposed to both conditions. Neither plasma adrenocorticotropic hormone (ACTH) nor corticosterone was altered by the treatment conditions. This study corroborated previous reports that ionizing radiation exposure increased plasma levels of 8-hydroxy-2'-deoxyguanosine (8-OHDG), but no effect was observed in animals co-exposed to chronic noise. Plasma big-endothelin-1 (Big ET-1) was significantly reduced in animals exposed to a combination of noise and X-rays. The results indicated that (1) adaptation to chronic noise appeared to occur at the level of the hypothalamic pituitary adrenal (HPA) response, in spite of a compromise in overall body weight gain; and (2) ionizing radiation exposure might alter systems activated by stressor exposure and/or act independently to influence health outcomes.

Monitoring of brain potassium with rubidium flame photometry and MRI

“…The safety of RbCl administration is supported by Fig. 3, which shows that during RbCl feeding the animals consistently gained weight (albeit more slowly than 5–6 g per day for intact Sprague‐Dawley rats of the same age in our study and in the literature (36)).…”

Chronic noise exposure in the spontaneously hypertensive rat

“…However, normotensive rats exposed to a similar paradigm showed very little changes in comparable measures. [ 6 ] Until more research works come out to disentangle some of these possibilities, our results need to be considered tentative and interpreted with caution. Our finding of lower plasma TNF-alpha is consistent with the effects that stressor exposure can have on this endpoint, but further research is required to determine the basis for reduced CRP levels among the noise-exposed animals.…”

“…Stressor exposure activates several physiological pathways that may be implicated in some of the purported health effects observed in individuals who are exposed to relatively high levels of environmental noise for several years, especially those that involve the cardiovascular system. [ 1 2 3 ] These pathways include alterations in the hypothalamic pituitary adrenal (HPA) axis with a consequent increase in adrenocorticotropic hormone (ACTH) and cortisol (corticosterone in rodents);[ 4 5 6 ] others have shown rats habituate to loud noises as evidenced by a gradual return to baseline in corticosterone levels by the fourth day of exposure. [ 7 ] Similarly, pro-inflammatory cytokines, such as interleukin 1 (IL-1), tumour necrosis factor (TNF)-alpha and interleukin 6 (IL-6) have been implicated in the stress response.…”

Cardiovascular Changes in Atherosclerotic ApoE-Deficient Mice Exposed to Co60 (γ) Radiation

“…The ratio of 3-nitrotyrosine to L-DOPA, which reflects an estimate of the competition between nitrative and oxidative reaction pathways, increased under both acute and chronic radiation exposure conditions (Figure 4C–D), and also exhibited a linear dose-response relationship with radiation exposure (p = 0.022). It is well known that ionizing radiation affects biological systems through formation of reactive oxygen species [42]. Induction of superoxide (O 2 .− ) formation and increased release of NO .…”