Inhibition of Ouabain-sensitive ATPase by the Saliva of Patients with Cystic Fibrosis of the Pancreas

Abstract

Extractobtained by asking each child to rinse his mouth with water, and A study has been made of the effect of saliva from children with cystic fibrosis of the pancreas (CFPI on various components of the ATP hydrolyzing enzyme system. The ouabain-sensitive ATPase activity of erythrocyte membranes prepared from intact erythrocytes preincubated with CFP saliva was 35 4 nmol P,/mg dry wt membrane suspension/hr, compared with 48 i 7 nmol P,/mg dry wt membrane suspension/hr when the erythrocytes were preincubated with control saliva. A calcium-activated component of ATPase was decreased from 202 30 nmol P,/mg dry wt membrane suspension/hr in erythrocytes preincubated with control saliva, to 151 17 nmol P,/mg dry wt membrane suspension/hr when the incubation was carried out with CFP saliva.In a second series of experiments, ultrafiltered saliva was added directly to an ATPase assay. The saliva from children with CFP brought about a mean decrease in ouabain-sensitive ATPase of 16% compared with control saliva. SpeculationInhibition of active cation transport at various sites in the body is one of the hallmarks of CFP. Electrolyte abnormalities in the salita of patients with CFP may result from the action of an ATPase inhibitory factor in the saliva which inhibits various components of ATPase in the ducts of the salivary glands. Such a factor could be similar or identical with the ciliotoxic factor identified by other investigators in the serum and saliva of patients with CFP.Children with C F P have been demonstrated to have a higher than normal concentration of sodium in mixed saliva (19). The reasons for this elevation of salivary sodium have not been defined. Mangos et a[. (14) have shown that retrograde perfusion of the rat parotid duct with C F P saliva resulted in a decrease in the rate of sodium reabsorption in the parotid duct, but were unable to demonstrate an effect of C F P saliva on (Na, K)-ATPase fro'm various tissues.The presumed decrease in the rate of sodium reabsorption in the salivary ducts of children with C F P represents only one aspect of a widespread disturbance in active membrane cation transport in children with this disease (9,10,17). We have reported a factor in the plasma of children with C F P which inhibits a ouabain-sensitive, sodium-potassium-activated component of ATPase from normal erythrocyte membranes (4). The action of a similar factor in the saliva of children with C F P could have been obscured in previous studies by the relatively high concentration of phosphorous normally present in the saliva. In this paper, we report the results of two series of experiments designed to study the effect of C F P saliva on an ATPase assay system. METHODSThe patients with C F P used in this study were attending the outpatient clinic of the Montreal Children's Hospital. They ranged in age from 5 to 15 years, were about equally divided as to sex, and had Shwachman scores ranging from 33 91. Mixed saliva was then giving him a biece of laboratory parafilm to chew. N o effort was made to record or con...

Renal Function in Patients with Cystic Fibrosis

“…Our data are compatible with a defect in sodium reabsorption located most probably in the proximal tubule. Whether this observation reflects the presence of a specific sodium trans port blocking factor [6] or is due to factors such as nutri tional state, pulmonary dysfunction or antibiotic toxicity remains unknown.…”

“…Erythrocyte NaK-ATPase activ ity was found to be normal in CF [2,3]: on the other hand, introduction of sweat or saliva, obtained from patients with CF, into rat parotid gland caused a significant reduction in sodium reabsorption [4,5]. Cole et al [6] were able to isolate from serum of patients with CF a factor with a molecular size in the range of 1,000-10,000 dalton which was found to inhibit the ouabain-sensitive fraction of NaK-ATPase. Such a factor could easily cross the glomerular barrier, and would therefore conceivably exert its inhibitory effects on sodium transport primarily in the proximal tubule.…”

Short Communication: Cystic Fibrosis “Factor(s)” Present Also in Sera of Shwachman's Pancreatic Insufficiency

“…There is, however, increasing evidence that abnormalities of water and electrolyte transport may underlie the dysfunction of exocrine glands in this disorder, and CF "factor(s)" have been implicated as being primary in pathogenesis (10)(11)(12). Such factor(s) have been reported in sweat, saliva, and serum (2,5,7,15,16,18,22) using a variety of in vitro techniques.…”