N-acetylcysteine L-lysinate Nacystelyn (L-NAC) is a newly synthesized mucolytic agent, of which the action in vivo has not been well defined. In six healthy mongrel dogs, the rheological properties of mucus, its mucociliary and cough clearability, and the transepithelial potential difference (PD) of the tracheobronchial epithelium were evaluated after placebo and L-NAC metered dose inhaler (MDI) aerosols. The principal index of mucus rigidity, log G*, decreased at all airway sites with L-NAC administration, i.e. the mucus became less rigid and more deformable (the overall change in G* was 0.29 log units, i.e. ca. twofold decrease). The viscoelasticity-derived mucus transportability parameters, mucociliary (MCI) and cough (CCI) clearability indices, increased with L-NAC MDI, particularly CCI, which predicts the effect of mucus rheology on cough clearability. PD increased significantly with L-NAC administration at all measurement sites, which appears to be a novel effect for a direct acting mucolytic agent. Tracheal mucus linear velocity (TMV) increased after L-NAC compared with placebo, as did the normalized frog palate transport rate (NFPTR). The increase in NFPTR was greater than that predicted from the mucus rheological properties alone, suggesting that L-NAC still resident in the collected mucus stimulated the frog palate cilia. The index of mucus flux, the collection rate in mg.min-1, was higher with L-NAC compared with placebo. From our results, we conclude that L-NAC shows potential benefit in terms of improving mucus rheological properties and clearability. It may act, in part, by stimulating the fresh secretion of mucus of lower viscoelasticity. The stimulation of mucociliary clearance could be related to ion flux changes, as indicated by the increase in PD.

Objective: With increasing life span osteoporosis becomes a more recognized problem in patients with cystic fibrosis (CF). The aim of this cross-sectional study in 75 adult patients with CF (mean age 25.3 years) was to assess the prevalence of low bone mineral density (BMD) by dual-energy x-ray absorptiometry (DEXA) and, for the first time, by quantitative ultrasound (QUS), and to identify predicting factors. Design and Methods: Bone status was assessed at the lumbar spine (L2-L4) and the femoral neck by DEXA, and at the calcaneus by QUS (stiffness index). These data were correlated with a variety of clinical and anthropomorphic variables. Biochemical markers of bone turnover such as osteocalcin, bone-specific alkaline phosphatase, crosslinks in urine, 25-hydroxy vitamin D (25-OH vitamin D), parathyroid hormone, calcium and free testosterone were determined by standard assays. Results: The mean BMD T score (^S.E.M.) was 21:4^0:17 at the lumbar spine, and 20:54^0:16 at the femoral neck. The mean T score of the calcaneal stiffness index was 20:83^0:19: Based on a lumbar spine T score ,22.5 by DEXA, 27% of the patients had osteoporosis. Multiple regression analysis showed that the forced expiratory volume in one second (FEV 1 ) and the use of oral glucocorticoids were independent predictors of low lumbar spine BMD, whereas body mass index (BMI) and the use of oral glucocorticoids were independent predictors of low femoral neck BMD. The stiffness index correlated moderately with BMD (0.49-0.62, P , 0:0001). QUS had a sensitivity and specificity of only 57% and 89% respectively for diagnosing 'osteoporosis' (based on a femoral neck T score ,22.5 by DEXA). Positive and negative predictive values were 36% and 95% respectively. Conclusions: Low BMD is frequent in adults with CF and is most strongly correlated with disease severity (BMI, FEV 1 ) and the use of glucocorticoids. Calcaneal QUS might help to screen out patients with a normal BMD, but sensitivity and specificity were not sufficiently high to replace DEXA in these patients.

The transfer of water across the airway epithelium is closely related to the transepithelial potential difference (PD). Thus, PD should be directly involved in the regulation of airway intraluminal water content and, by extension, mucus rheology. Experiments by Boucher and co-workers (J Appl Physiol, 1980; 48: 169; and 1981; 51: 706) indicated that the values of PD in the small airways of dogs were considerably lower than in the trachea or mainstem bronchus. This fact suggests that water is increasingly removed from the airway lumen in the cephalad direction, and provides a possible mechanism whereby airway flooding is avoided as the total airway cross-section diminishes mouthward. We investigated this possibility by collecting and analysing mucus from the small airways and trachea of anaesthetized dogs and comparing our findings with measurements of PD. Mucus was collected on a cytology brush placed against the wall of the airway. Tracheal samples were taken from the lower lateral or anterior trachea, while small airway samples were taken from a 6th or 7th generation bronchus, chosen at random from either side. Measurements of PD were made at comparable sites. The mucus was analysed for its viscoelastic properties using the magnetic microrheometer technique. PD in the 6th-7th generation bronchus was significantly less than in the lower trachea (4.1 +/- 1.3 vs 17.2 +/- 7.1 mV). The rigidity of mucus collected from the small airways (log mechanical impedance (G*) at 100 rad.s-1) was significantly less than in the trachea (2.81 +/- 0.22 vs 3.01 +/- 0.29).(ABSTRACT TRUNCATED AT 250 WORDS)