Elevating dietary salt exacerbates hyperpnea-induced airway obstruction in guinea
pigs.
Mickleborough, Timothy D., Robert W. Gotshall, Jann Rhodes, Alan Tucker, and Loren
Cordain.
1School of Sport Science, PE and Recreation, University of Wales Institute, Cardiff,
Wales, CF23 6XD United Kingdom; 2Department of Exercise and Health Science and
3Department of Physiology, Colorado State University, Fort Collins, Colorado
80523
APStracts 8:0269A, 2001.
Previous studies have indicated that increased dietary NaCl consumption worsens
postexercise pulmonary function in humans with exercise-induced asthma (EIA). It has
been suggested that EIA and hyperpnea-induced airway obstruction (HIAO) in guinea
pigs (an animal model of EIA) are mediated by similar mechanisms. Therefore, the
purpose of this study was to determine whether altering dietary NaCl consumption also
exacerbated HIAO in guinea pigs. Furthermore, the potential pathway of action of dietary
NaCl was investigated by blocking leukotriene production during HIAO in guinea pigs.
Thirty-two male Hartley strain guinea pigs were split into two groups. One group (n =
16) of animals ingested a normal-salt diet (NSD) for 2 wk; the other group (n = 16)
ingested a high-salt diet (HSD) for 2 wk. Thereafter, animals were anesthetized,
cannulated, tracheotomized, and mechanically ventilated during a baseline period and
during two dry gas hyperpnea challenges. After the first challenge, the animals were
administered either saline or nordihydroguaiaretic acid, a leukotriene (LT) inhibitor.
Bladder urine was analyzed for electrolyte concentrations and urinary LTE4. The HSD
elicited higher airway inspiratory pressures than the NSD (P < 0.001) postchallenge.
However, after infusion of the LT inhibitor and a second hyperpnea challenge, HIAO was
blocked in both diet groups (P < 0.001). Nonetheless, the HSD group continued to
demonstrate slightly higher Ptr than the NSD group (P < 0.05). Urinary LTE4 excretion
significantly increased in the HSD group compared with the NSD group within treatment
groups. This study demonstrated that dietary NaCl loading exacerbated the development
of HIAO in guinea pigs and that LT release was involved in HIAO and may be
moderated by changes in dietary NaCl loading.
Received 14 December 2000; accepted in final form 23 April 2001
APS Manuscript Number A1174-0.
Article publication pending J Appl Physiol
ISSN 1080-4757 Copyright 2001 The American Physiological Society.
Published in APStracts on 18 June 2001