EFFECT OF IN-VIVO CORTICOSTEROIDS ON NA+ TRANSPORT ACROSS AIRWAY EPITHELIA

We have investigated the role in vivo of mineralocorticoid and glucoco rticoid hormones in regulating the rate of electrogenic amiloride-sens itive Na+ absorption across murine airway tissue studied in vivo (nasa l potential difference) and in vitro (Ussing chambers). We found that elevating the plasma aldosterone concentration 10-fold (low-Na+ diet) had no significant effect on amiloride-sensitive Na+ absorption across tracheal or nasal epithelia. High doses of dexamethasone for 1 wk lik ewise did not change the rate of amiloride-sensitive Na+ absorption ac ross airway epithelia. In contrast, both hormonal manipulations elevat ed the rate of colonic Na+ absorption. Furthermore, adrenalectomy (bot h normal and cystic fibrosis mice) also failed to alter Na+ absorption across airway epithelia. We conclude that, in vivo, neither the miner alocorticoid nor the glucocorticoid hormones significantly regulate th e rates of amiloride-sensitive electrogenic Na+ absorption across airw ay epithelia in the adult mouse.