Figure 8.

Effects of neomycin on the cold-induced production of PtdOH (in absence or presence of added excess nonradioactive PO₄³) and InsP₃ during an exposure at 0°C. InsP₃ (circle), PtdOH in absence of nonradioactive PO₄³⁻ (square), and PtdOH in the presence of 3 mm of nonradioactive PO₄³⁻ (diamonds). Values are expressed as a percentage of values obtained in nontreated cells (mean of three determinations ± sd). Neomycin was 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 measurement, 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. PtdOH and InsP₃ were quantified as detailed in “Materials and Methods.”