Summary

Background and objective: An anti-inflammatory effect of α2-adrenoreceptor agonists has been suggested. Phospholipase A2 is a key enzyme in the production of precursors of inflammatory lipid mediators. The aim of the present study was to investigate the effect of clonidine on phospholipase A2 activity in an established in vitro model. Methods: Human being platelet membranes containing active phospholipase A2 were exposed to buffer control or to three increasing concentrations of clonidine. Phospholipase A2 was measured by a radioisotope technique. Results: A massive increase in phospholipase A2 activity was measured after clonidine exposure leading to final values of 92.5 ± 3.1 pmol mg protein−1 min−1 (4.5-fold higher than control values; P ≤ 0.01 vs. control). After clonidine exposure the maximal reaction velocity increased, while the Michaelis–Menten constant did not change. The Lineweaver–Burk representation suggested an interaction of clonidine with the phospholipase A2–substrate complex as well as the phospholipase A2 molecule. Conclusion: We conclude that the putative anti-inflammatory effect of clonidine was not caused by inhibition of phospholipase A2.

Extension of recurrent respiratory papillomatosis (RRP) to the lower airway in children is life-threatening and an extremely difficult condition to treat. We present the case of a seven-year-old girl with progressive RRP since the age of two. Repeated CO2 laser treatment and interferon-alpha treatment could not prevent tracheotomy and spread to the trachea. We used argon plasma coagulation (APC) with flexible endoscopy for the first time for the treatment of RRP. APC gives a controlled limited penetration into the tissue and good control of bleeding. There is no carbonization or vaporization which makes it a suitable method for the treatment of lower airway RRP. After a few treatments with APC, we gained very good control of the disease with no side-effects or complications. The described application of APC seems to be a promising way to treat lower airway RRP.