We found that vanadate-induced 45Ca2+ uptake by red cells is maximal at 25°C. At this temperature, the Cai-induced increase of the K+ permeability (the Gardos effect) shows a lag (up to 8 min) which is not observed at 37°C. This cannot be explained by the lack of availability of Ca2+ for the Ca2+-activated K+ channel, and suggests that its activation by Ca2+ is mediated by a temperature-dependent mechanism which remains unknown so far. The lag is not observed when the Gárdos effect was initiated by propranolol. This shows that the putative temperature-dependent step is different from chloride transport.
