Increased kallikrein content of saliva from patients with cystic fibrosis of the pancreas. A theory for the pathogenesis of abnormal secretions.

Abstract

Extract: An investigation of the bradykinin system in cystic fibrosis of the pancreas was undertaken because of the potential role of bradykinin in the function of glandular tissues and in the mediation of electrolyte transport. Patients with cystic fibrosis of the pancreas (CFP) and control; subjects (CS) were studied for evidence of kininase and kallikrein acitities were assayed by means of a modified Schultz-Dale apparatus utilizing the uterus of rats in estrus. The bradykinin assay detected as little as 0.01 μg bradykinin (4 × 10-4 μg/ml bath solution). The height of uterine contraction was proportinal to the logarthmic concentration of bradykinin with maximun contraction occurring with 1–10 μg bradykinin. Free bradykininlike activity in urine, saliva or plasma specimens from 11 patients was the same as that from 21 normal controls. In saliva specimens from CFP or CS no bradykininlike activity was detected, whereas in urine there was slight activity in approximately 60% of the samples. Fresh heparinized plasma of both patients and control subjects developed spontaneous bradkinin activity when added to the muscle bath; this type of activity could be prevented by shaking the plasma with glass beads and incubating at 37° for 30 min. All of the ‘glass-shaken’ plasma specimens developed normal-appearing bradykinin activity when activated by salivary kallikrein. The presence of bradykininlike activity in urine was unrelated to proteinuruia since none of the patients with activity in their urine had detectable prrteinuria. Five other patients with the nephrotic syndrome and heavy proteinuria had no bradykininlike activity in their urine. Plasma samples from 11 patients and 13 control subjects contained kininase that deacivated 10 μg synsthetic bradykinin within 10 min. In each sample, salivary-induced bradykinin was similarly deactivated by the plasma kininase within 12 min. Urinary-induced bradykinin, however, was still present in many of the urine-plasma mixtures after 12 min, but in only two (one CFP and one CS) was there residual bradykinin activity 22 min. Salivary kininase activity was detected in both patients and control subjects. Inactivation of 10 μg of synthetic bradykinin by 0.5 ml of saliva was much slower than that by plasma kininase and usually required up to 90 min. No kininase activity was detected in urine of patients or control subjects. Slight kallikrein activity was detected in urine of both groups. Kallikrein mesured 1.95 ± 1.7 units in 11 control subjects compared with 1.59 ± 0.42 units in 8 patients. This difference was not significant. The saliva from 11 patients showed a significantly greater kallikerin content (19.3 ± 13 units) than that from 18 control subjects (7.2 ± 8 units). In patients however, protein content was greater than in control subjects, and kallikrein activity correlated directly with the total protein content of the saliva (r = 0.671; p < 0.005). The results obtained from kallikrein assays with saliva suggest the presensce of an inhibitor to kallikrein in many of the specimens from CFP and CS, since the formation of bradykinin did not increase with higher concentrations of salica. Storage of the saliva at 0 or 4° for approximately 1 week resulted in loss of this inhibitory effect in most instances, and a linear relation between the amount of saliva and the resultant bradykinin activity at all concentrations of sailva was observed. This evaluatio of the bradykinin-forming system in plasma, urine and saliva failed to yield any evidence for excessive fromation or impaired inactivation of bradykinin; however, mixed salica of patients with cystic fibrosis of the pancreas was found to contain significantly higher kallikrein activity than that of normal controls. It is likely that this increase in salivary kallikrein accompanies the overall increase of organic constituents known to exist in saliva of patients with this disease. It is postulated that the abnormal secretions that occur in cystic fibrosis of the pancreas may result from excessive cholinergic stimulation in the presence of cholinergic blockade. This would result in an overall inceeae of organic constituents in the secreton, includinf kallikrein, and in a low secretory volume. Speculation: The results of this study failed to demonstrate a defect the bradykinin systern that could be responsible for the abnormal secreations associated with cystic fibrosis of the pancreas. It is possible, however, that an abnormality occurs at the celluar level, and further investigation of this system is indicated.