GTP-dependent Ca2+ release from rat liver microsomes Vesicle fusion is not required

AbstractThe GTP-dependent calcium release from rat liver microsomes is known to be promoted in the presence of colloids like polyethyleneglycol (PEG), polyvinylpyrrolidine, or albumin. Dawson et al. [(1987) Biochem. J. 244, 87–92] using the ‘fusogen’ PEG have concluded that both GTP-induced calcium efflux and the enhancement of InsP3-promoted calcium release in the presence of GTP could be attributed to a GTP-dependent vesicle fusion. Here, using the more physiological colloid albumin we report that GTP-induced calcium release from rat liver microsomes may not be linked to vesicle fusion