Rossier M F, Capponi A M, Vallotton M B
Division of Endocrinology, University Hospital, Geneva, Switzerland.
Biochem J. 1987 Jul 1;245(1):305-7. doi: 10.1042/bj2450305.
The metabolism of [3H]inositol 1,4,5-trisphosphate ([3H]Ins(1,4,5)P3) was studied in permeabilized rat aortic smooth-muscle cells. Addition of [3H]Ins(1,4,5)P3 to the leaky cells led to formation of several labelled metabolites. Amounts of [3H]inositol bisphosphate and [3H]inositol 1,3,4,5-tetrakisphosphate ([3H]InsP4) reached a maximum within 2 min of incubation, whereas production of [3H]inositol monophosphate and [3H]inositol 1,3,4-trisphosphate ([3H]Ins(1,3,4)P3) was delayed. Formation of InsP4 and Ins(1,3,4)P3 was Ca2+-sensitive in the physiological intracellular range (0.06-5 microM), showing a maximum at 1 microM-Ca2+. A correlation between the formation of InsP4 and that of Ins(1,3,4)P3 was observed, suggesting that the former is the precursor of the latter. These results suggest that, in vascular smooth-muscle cells, Ins(1,4,5)P3 is metabolized via two distinct pathways: (1) a dephosphorylation pathway, leading to formation of inositol bis- and mono-phosphate; and (2) a Ca2+-sensitive phosphorylation/dephosphorylation pathway, involving formation of InsP4 and leading to formation of Ins(1,3,4)P3.
在通透的大鼠主动脉平滑肌细胞中研究了[3H]肌醇1,4,5 -三磷酸（[3H]Ins(1,4,5)P3）的代谢。向有渗漏的细胞中加入[3H]Ins(1,4,5)P3会导致形成几种标记代谢物。[3H]肌醇二磷酸和[3H]肌醇1,3,4,5 -四磷酸（[3H]InsP4）的量在孵育2分钟内达到最大值，而[3H]肌醇单磷酸和[3H]肌醇1,3,4 -三磷酸（[3H]Ins(1,3,4)P3）的产生则延迟。在生理细胞内钙浓度范围（0.06 - 5微摩尔）内，InsP4和Ins(1,3,4)P3的形成对Ca2 +敏感，在1微摩尔 - Ca2 +时达到最大值。观察到InsP4的形成与Ins(1,3,4)P3的形成之间存在相关性，表明前者是后者的前体。这些结果表明，在血管平滑肌细胞中，Ins(1,4,5)P3通过两条不同的途径代谢：（1）去磷酸化途径，导致形成肌醇二磷酸和单磷酸；（2）Ca2 +敏感的磷酸化/去磷酸化途径，涉及InsP4的形成并导致Ins(1,3,4)P3的形成。
