| Abstract: | When 3H]inositol-prelabelled N1E-115 cells were stimulated with carbamylcholine (CCh) (100 microM), high K+ (60 mM), and prostaglandin E1 (PGE1) (10 microM), a transient increase in 3H]inositol pentakisphosphate (InsP5) accumulation was observed. The accumulation reached its maximum level at 15 s and had declined to the basal level at 2 min. CCh, high K+, and PGE1 also caused accumulations of 3H]inositol 1,4,5-trisphosphate Ins(1,4,5)P3], 3H]inositol 1,3,4,6-tetrakisphosphate Ins(1,3,4,6)P4], and 3H]inositol hexakisphosphate (InsP6). Muscarine and CCh induced accumulations of 3H]Ins(1,4,5)P3, 3H]-Ins(1,3,4,6)P4, 3H]InsP5, and 3H]InsP6 with a similar potency and exerted these maximal effects at 100 microM, whereas nicotine failed to do so at 1 mM. With a slower time course, CCh, high K+, and PGE1 caused accumulations of 3H]-inositol 1,3,4-trisphosphate Ins(1,3,4)P3] and 3H]inositol 1,3,4,5-tetrakisphosphate Ins(1,3,4,5)P4]. In an N1E-115 cell homogenate, 3H]Ins(1,4,5)P3, 3H]Ins(1,3,4,5)P4, and 3H]Ins(1,3,4)P3 were converted to 3H]InsP5 through 3H]-Ins(1,3,4,6)P4. The above results indicate that Ins(1,3,4,6)P4, InsP5, and InsP6 are rapidly formed by several kinds of stimulants in N1E-115 cells. |
