DIFFERENTIAL EXPRESSION AND IMMUNOHISTOCHEMICAL LOCALIZATION OF THE PHENOL AND HYDROXYSTEROID SULFOTRANSFERASE ENZYME FAMILIES IN THE DEVELOPING LUNG

Reversible sulphation, catalysed by sulphotransferases and sulphatases , of biologically active compounds such as androgens and oestrogens is a sensitive mechanism for regulating their bioavailabilty, and we hav e previously hypothesised that this process plays a significant role i n the regulation of human fetal lung development. Sulphation is also a major detoxification re action, contributing significantly to the bod y's chemical defence mechanism. We have used qualitative and semiquant itative immunological studies to determine the temporal expression and localisation of phenol and hydroxysteroid sulphotransferases during h uman lung development. Our results show that in the early fetal lung, phenol sulphotransferase expression is at its highest, and is most wid ely distributed throughout the developing respiratory epithelium. With later development, expression levels decrease and become predominantl y restricted to the more proximal airways. In contrast, hydroxysteroid sulphotransferase is present only at very low levels in the early-ges tation lung but expression increases rapidly through gestation to reac h an apparent peak by 1 year postnatal age. The proximal-to-distal gra dients of phenol and hydroxysteroid sulphotransferase expression were similar in mature respiratory epithelium, with immunoreactivity in cil iated cells, non-ciliated secretory cells and basal cells, but with no apparent expression in mucus-secreting cells. These studies provide s upporting evidence for the hypothesis that hydroxysteroid sulphotransf erase, an androgen-inactivating enzyme, contributes to the role of and rogens in retarding the maturation of human lung in utero.