Figure 9.

Effects of LaCl₃ and EGTA on the cold-induced production of PtdOH in presence of added cold PO₄³⁻ and InsP₃ during an exposure at 0°C. Values are expressed as a percentage of values obtained in nontreated cells (mean of three determinations ± sd). Chemicals were added 15 min prior to the cold treatment. When necessary, 3 mm PO₄³⁻ was also added. For PtdOH measurement, phospholipids were labeled in presence of 53 MBq L⁻¹ [³³P]-PO₄³⁻ for 2 h at 22°C. Lipids were extracted 10 min after the beginning of the cold treatment and were separated by a TLC using the acidic solvent system. For InsP₃ measurements, biological reactions were stopped by the addition a 0.2-volume of ice-cold 20% (w/v) perchloric acid 3 min after the beginning of the cold treatment.