Effect of Noise on Microvascular Integrity in Laboratory Rats

Housing rats in an environment with high personnel activity increases microvascular leakiness to albumin in the mesenteric microcirculation and causes mast cell degranulation. In this study, rats were exposed to daily 15-min episodes of 90-dB SPL noise to determine whether similar effects occurred and whether vitamin E with α-lipoic acid or Traumeel (a homeopathic anti-inflammatory–analgesic) reduced these effects. Groups of rats fed a control diet (1000 IU/kg vitamin E) only, the control diet with Traumeel, or a diet with 10,000 IU/kg vitamin E and 1.65 g/kg lipoic acid were exposed to daily noise for 3 to 5 wk; a fourth group of rats, fed control diet, was housed with no excess noise. The rats were anesthetized, the superior mesenteric artery cannulated, and a portion of the microvasculature perfused for 1 min with fluoroscein isothiocyanate–albumin before fixing for microscopy. All groups exposed to excess noise had significantly more leaks per venule length and greater leak area per venule length than did the quiet group. However, the number and area of leaks in the rats that received Traumeel or vitamin E were significantly smaller than those in rats exposed to noise only. In addition, mast cell degranulation was significantly lower in rats given Traumeel. Thus exposure of rats to excessive noise produces structural damage in the mesenteric microvasculature that is significantly reduced by dietary supplements.