Regulation of Absorption in the Human Sweat Duct

Abstract

It is now well established that cystic fibrosis is expressed physiologically as defects in certain fluid and electrolyte transport systems that are highly active in exocrine tissues (Quinton, 1983; Knowles et al., 1983; Kopelman et al., 1982; Orlando et al., 1989). More specifically, two basic physiological defects have been demonstrated directly in at least two of the organ systems characteristically affected in cystic fibrosis -the sweat glands and the airways. The two defects in these affected epithelia appear as 1) an inherently reduced permeability to Cl-(Quinton, 1983; Widdicombe et al., 1985; Knowles, 1983), and 2) a failure of fluid secretion to respond to β-adrenergic stimulation (Sato and Sato, 1984; Widdicombe et al., 1985). The refractory response to β-adrenergic stimulation is most clearly seen in secretory functions and is thought to be due to an inactivatable chloride channel (Welsh, 1986; Frizzell, 1986). While other defects have been associated with cystic fibrosis, e.g., increased Na⁺ permeability (Knowles et al., 1983; Boucher et al., 1986; Willumsen and Boucher, 1989), abnormal sulfate metabolism (Cheng et al., 1985), and abnormal calcium levels (Sorcher and Beslow, 1982; Shapiro et al., 1980), the basic physiological abnormality in the disease seems to center upon chloride impermeability.