Pleural mesothelium lubrication after phospholipase treatment

• Pleural kinetic friction (μ) increased after short phospholipase treatment.
• This increase, without cell disruption, was removed by hyaluronan or sialomucin.
• These molecules removed increase of μ even with cell disruption.
• After phospholipase μ decreased with increase in sliding velocity.
• Hyaluronan before phospholipase treatment protected from the enzyme.

Coefficient of kinetic friction (μ) of rabbit pleural mesothelium increased after short treatment of specimens with phospholipase C. This increase was removed by addition of a solution with hyaluronan or sialomucin, as previously shown in post-blotting Ringer or after short pronase treatment. After phospholipase μ decreased with increase in sliding velocity, but at highest velocity it was still greater than control; this difference was removed by addition of hyaluronan or sialomucin, as in post-blotting Ringer or after short pronase treatment. Hyaluronan placed on specimen before phospholipase treatment reduced increase in μ by protecting phospholipids from enzyme, as shown by others for alveolar and synovial phospholipids. Samples of parietal pleura stained with silver nitrate showed that mesothelial cells were not disrupted by short phospholipase treatment. Instead, they were disrupted if this treatment was preceded by a short pronase treatment; but even after this disruption addition of hyaluronan or sialomucin brought μ back to control.