SUMMARY: accumulated glycerol at a rate of 200 fmol per cell h, when subjected to a hyperosmotic shock of 0.930 osmol 1 with NaCl or mannitol. In alkaline media, a slight inhibition of the osmotic response, to 130 fmol per cell h at pH 9, was found. Acetate or ammonium ions markedly decreased osmoinduced glycerol synthesis under pH conditions where the uncharged form of these agents was present at concentrations exceeding 2 mM. The proton translocators dinitrophenol (DNP) (0.3-1 mM) and carbonyl cyanide -chlorophenyl-hydrazone (CCCP) (0.01, 0.03 and 0.05 mM) disturbed the metabolic response at all pH values tested. Also, DNP disturbed glycerol retention in low pH media, whereas CCCP did not affect the glycerol level under iso-osmotic conditions. The osmoinduced glycerol synthesis was blocked almost completely in the presence of monovalent cation ionophores such as nigericin (0.01 mM) and monensin (10 pg ml) but not by the K ionophore valinomycin (0.01 mM). With all the ionophores investigated, a correlation was found between decreasing glycerol and ATP contents, indicating that glycerol synthesis requires ATP. The results are discussed in relation to the regulation of glycerol metabolism under different osmotic conditions.


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