The Clara cell: secretory and developmental studies in the rat.

Clara cells are non-ciliated epithelial cells located mainly in small conducting airways. They give rise to ciliated cells and are also thought to secrete components of the extracellular layer lining small conducting airways. Using morphometry and electron microscopy we have shown that secretion by Clara cells in rats is stimulated by a beta-adrenergic agent, by prostacyclin and by large tidal volumes. The effect of large tidal volume ventilation breathing on secretion is blocked by indomethacin (an inhibitor of prostaglandin synthesis), but it is not blocked by cholinergic blockade or by beta- or alpha-adrenoceptor antagonists. More recently we have shown that Clara cells in rats are immature at birth, rapidly gain maturity within the first postnatal week and that maternal undernutrition delays the attainment of maturity; glucagon given intraperitoneally to the rat fetus just before term accelerates the attainment of maturity; glucagon given intraperitoneally to the rat fetus just before term accelerates the attainment of maturity.