HYALURONAN ACTIVATES CALCIUM-DEPENDENT CHLORIDE CURRENTS IN XENOPUS OOCYTES

Hyaluronan (5 mg/ml) activated an oscillatory inward current of up to 200 nA in oocytes held voltage-clamped at -60 mV. The reversal potenti al of the current was -25 +/- 1 mV (n = 5), close to the Cl- equilibri um potential for oocytes. The response was dose-dependent over the con centration range 0.2-10 mg/ml, independent of external Ca2+ but abolis hed by injection of EGTA, a Ca2+ chelator. In addition, hyaluronan sen sitivity in oocytes was seasonal with 91% of the responses occurring b etween June and December. Pre-heating hyaluronan to >50 degrees C redu ced the response; at 70-85 degrees C the response was lost. Cooling th e heated hyaluronan, however, restored the activity. Hyaluronan which had been previously digested with 10 mg/ml hyaluronidase for 1-7 h (at 37 degrees C) activated smaller currents: for digestions >7 h the cur rent-activating ability of hyaluronan was abolished. The results are d iscussed in relation to possible signal transduction pathways involvin g hyaluronan. (C) 1997 Federation of European Biochemical Societies.