Effect of inositol 1,4,5‐trisphosphate and GTP on calcium release from pituitary microsomes

[摘要]

Microsomal vesicles from bovine anterior pituitary accumulate Ca²⁺ and maintain a steady-state ambient Ca²⁺ level of 200 nM. IP₃ and GTP both induce calcium release from the microsomal vesicles. The effect of IP₃ is inhibited by polyethylene glycol (PEG), and the effect of GTP is absolutely dependent on PEG. Half-maximal effect of IP₃ (without PEG) is 0.26 μm, the maximal calcium release attaining 7% of the A23187-releasable pool. The same values for GTP (in the presence of PEG) are 80 μM and 10%, respectively. GTP potentiates the effect of IP₃. This potentiation is not mediated by protein phosphorylation.

[学科分类] 生物化学/生物物理

[关键词] GTP;Inositol trisphosphate;Ca2+ release;Microsome;Polyethylene glycol;Protein phosphorylation;EC50;concentration required for half-maximal effect;IP3;inositol 1;4;5-trisphosphate;PEG;polyethylene glycol