THE EFFECT OF DIETARY-SODIUM ON THE CONCENTRATIONS OF VASOACTIVE-INTESTINAL-PEPTIDE IN PLASMA AND LUNG

Study objectives: In this study, we sought to determine whether change s in the concentration of vasoactive intestinal peptide (VIP) in the l ung might explain the increase in bronchial reactivity associated with high sodium diets. Design: Male Sprague-Dawley rats, eight in each gr oup, were placed on low-sodium, normal-sodium, or high-sodium diets an d distilled drinking water ad libitum for 7 days, On the day of study, blood was sampled to determine plasma VIP concentration and the lungs were harvested and snap frozen in liquid nitrogen, VIP was measured i n plasma and tissue extracts by radioimmunoassay. Results: The MP conc entrations in both lung and plasma varied with dietary sodium, Plasma VIP level was significantly higher in the rats that had received the l ow-sodium diet (51.45+/-7.35 pmol L(-1)) than in the rats that had rec eived the high-sodium diet (29.84+/-6.83; p<0.05), In the lung, VIP le vel was greater in the rats that had received the normal-sodium diet ( 378.13+/-41.68 fmol/g) than in rats that had received either the low-s odium diet (137.30+/-26,1 1 fmol/g; p<0,0005) or the high-sodium diet (182,64+/-28.63 fmol/g; p<0.005). Conclusions: The lower plasma and pu lmonary concentrations of VIP observed in rats that had received a hig h-sodium diet suggest that VIP may play a role in the increased bronch ial reactivity reported with this diet.