Evidence against a specific effect of serum from patients with cystic fibrosis on sodium-dependent glucose transport in the rat jejunum.
Sera from patients with cystic fibrosis of the pancreas (CF) and normal human sera were assayed for the ability to inhibit sodium-dependent glucose transport in rat brush-border membrane vesicles. Fresh CF and age- and sex-matched control sera were both inhibitory when compared to physiologic saline. The inhibition by CF serum was 44 +/- 13% (mean +/- SD) at a final serum concentration of 6.7%, 67 +/- 34% at 10% serum, and 68 +/- 28% at 20% serum. The ratio of the inhibition of CF sera compared to that of control sera was 1.00, 0.78, and 0.93 at 6.7, 10, and 20% serum concentrations, respectively. Although a slightly greater inhibition by CF serum was observed at a concentration of 10%, this is probably not significant because no difference could be detected at a concentration of 20% serum. Glucose transport in the presence of serum was sensitive to phlorizin indicating that the residual glucose transport was proceeding by the sodium-dependent glucose transport system. These findings suggest that CF serum does not specifically inhibit the sodium-dependent glucose transport system. The intravesicular space accessible to glucose was reduced in the presence of CF or control serum. Fresh CF serum was 1.4 times more effective than fresh control serum (P less than 0.01). The presence of substantial vesicle-shrinking activity in control serum indicates that this activity cannot be considered specific for CF.
D000818:Animals; D003550:Cystic Fibrosis / Q000097:blood*; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007583:Jejunum / Q000378:metabolism*; D008297:Male; D008871:Microvilli / Q000378:metabolism; D010695:Phlorhizin / Q000494:pharmacology; D051381:Rats; D012964:Sodium / Q000494:pharmacology*
D012964:Sodium; D010695:Phlorhizin; D005947:Glucose