Saliva from patients with cystic fibrosis inhibits amiloride-sensitive sodium transport.
A factor is present in the saliva and sweat from patients with cystic fibrosis (CF) which inhibits the reabsorption of sodium in the ducts of the salivary and sweat glands. Inasmuch as the physiology of sodium absorption is similar in salivary ducts and the distal colon, we have examined the sensitivity of the sodium absorption in the rat colon to saliva from CF patients. Sodium absorption by the rat colon, estimated as the shortcircuit current, was inhibited by saliva from both patients with CF and normal volunteers. However, only with CF saliva was the inhibition consistently proportional to the saliva concentration. Furthermore, the inhibitory activity of CF saliva was greater than the inhibition observed with saliva from age- and sex-matched controls (percentage of inhibition: CF = 20.1 +/- 2.2, and controls = 14.9 +/- 2.1; P < 0.02), and the inhibition of the colonic shortcircuit current was proportional to the activity measured by the ductal retrograde perfusion assay with the rat parotid gland (linear correlation coefficient = 0.634; P < 0.005). This latter assay is an accepted assay for CF factor activity. We conclude that the CF factor present in saliva probably interacts in a reversible manner with the amiloride-sensitive sodium transport system which is present in all sodium scavenging epithelia. The rat colon is a promising assay system for CF factor activity because the electrical measurements permit a rapid quantitative estimate of activity and a single piece of tissue can be used to measure the activity of several saliva samples.
D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D003106:Colon / Q000502:physiology; D003550:Cystic Fibrosis; D004594:Electrophysiology; D066298:In Vitro Techniques; D007408:Intestinal Absorption / Q000187:drug effects*; D008297:Male; D011719:Pyrazines / Q000494:pharmacology*; D051381:Rats; D012463:Saliva / Q000032:analysis; D012964:Sodium / Q000032:analysis / Q000172:deficiency / Q000502:physiology*
D011719:Pyrazines; D000584:Amiloride; D012964:Sodium