Non-respiratory function of lungs -

Ans. is 'b' i.e., Sodium balance * One of the most important metabolic (non-respiratory) function of lungs is activation of relatively physiologically in active decapeptide angiotensin I to 50 times more potent (active) vasoconstrictor, pressor (|BP), aldosterone stimulating octapeptid angiotensin II by extracellular ACE on the surface of endothelial cells in pulmonary circulation.* Asa part of renin-angiotensin-aldesterone system, lungs indirectly regulate sodium and water balance (and BP). However, lungs also directly affect Na+ balance via epithelial Na+ channels (E NaCs). Absorption of excess fluid from alveolar lumen and airways require active transepithelial transport of Na+ by ENaCs (mainly of alveolar type II and possibly type I cells).