Exposure to repeated low-level formaldehyde in rats increases basal corticosterone levels and enhances the corticosterone response to subsequent formaldehyde

Low-level exposure to volatile organic compounds may produce symptoms in hu mans reporting multiple chemical sensitivity (MCS) through altered hypothal mic-pituitary-adrenal (HPA) axis functioning. We determined whether repeate d formaldehyde (Form) exposure would alter corticosterone (CORT) levels in a rat model of MCS. Male Sprague-Dawley rats were given acute chamber expos ures to Air or Form (0.7 or 2.4 ppm), and trunk blond was collected 20 or 6 0 min later. All groups showed increased CORT levels above naive basal leve ls at 20 min and a return to baseline by 60 min, with no differences betwee n treatment groups. The second experiment examined the effect of repeated F orm exposure (1 h/dayX5 days/weekX2 or 4 weeks) on basal CORT levels and af ter a final challenge. Basal CORT was increased above naive values after 2 week exposure to Air or 0.7 ppm Form. By 4 week, CORT levels in the Air gro up returned to naive values, but remained elevated in the 0.7 ppm Form grou p. There were no differences in basal CORT levels among either 2.4 ppm expo sed groups. After a final Air or Form challenge, the 2 and 4 week Air and 0 .7 ppm Form groups had elevated CORT levels similar to their acute response , while the 2 and 4 week 2.4 ppm Form groups had elevated CORT levels compa red to their acute response, indicating enhanced reactivity of the HPA axis to subsequent Form. These findings suggest that altered HPA axis functioni ng occurs after repeated low-level Form exposure, and may have implications for mechanisms mediating MCS in humans, (C) 2001 Published by Elsevier Sci ence B.V.