Heparin inhibits the inositol 1,4,5‐trisphosphate‐induced Ca²⁺ release from rat liver microsomes

Abstract

Inositol 1,4,5‐trisphosphate (Ins (1,4,5)P3)‐stimulated Ca2+ release is inhibited by low concentrations of heparin (IC50=4.5 μg/ml). GTP‐stimulated Ca2+ release is unaffected at a heparin concentration of 16 μ/ml. Addition of heparin after Ins (1,4,5)P3 causes the rapid re‐uptake of Ins (1,4,5)P3‐releasable Ca2+.

High‐affinity inositol 1,3,4,5‐tetrakisphosphate receptor from cerebellum: solubilization, partial purification and characterization

“…Heparin suppresses high-af~~ty Ins-P3 binding [ 12,151 and blocks Ins-P3-induced Ca2+ release [ 16,171. These results have been exploited frequently for using heparin as an experimental tool in the following context: disappearance of a cellular effect after injection of heparin was taken as evidence that Ins 1,4,5-P3 was involved in the activation process [IS].…”

Rat brain endoplasmic reticulum calcium pools are anatomically and functionally segregated.

“…The discrepancy in the total amount of calcium taken up between experiments. These parameters were adjusted to limit the breakdown of IP3 and the inhibition of IP3 binding by higher Ca2+ levels (Worley et al, 1987b is largely prevented by heparin, an established antagonist of IP3 receptor binding (Worley etal., 1987b) and IP3-induced calcium release (Cullen et al, 1988;Ghosh et al, 1988). The similar inositol phosphate specificity for 45Ca2' accumulation in brain slices, IP3 receptor binding (Worley et al, 1987b), and IP3 release of calcium in numerous other systems Ghosh et al, 1989;Irvine, 1989;Nahorski, 1989;Ferris et al, 1989) (Worley et al, 1987a;1989) closely resembles the IP3 sensitive pools of 45Ca2+ ( Figure 4).…”

“…The initial accumulation of 45Ca2+ into the endoplasmic reticulum involves the calcium ATPase, which is unaffected by IP3 (Delfert et al, 1986;Henne and Solung, 1986). Heparin, an established antagonist of IP3-induced calcium release (Cullen et al, 1988;Ghosh et al, 1988) and IP3 receptor binding (Worley et al, 1987b), also has no effect on calcium uptake by itself but is able to reverse the effect of IP3 (Table 1). Moreover, in several tissues IP3 has been shown to release nonmitochondrial pools of calcium and not to affect initial calcium uptake (Berridge, 1987;Berridge and Irvine, 1989).…”

Decavanadate displaces inositol 1,4,5-trisphosphate (IP3) from its receptor and inhibits IP3 induced Ca2+ release in permeabilized pancreatic acinar cells

“…A useful tool to characterize the IP3 receptor is heparin. It inhibits binding of IP3 to its receptor [5][6][7] and IP3 induced cl+ release [8][9][10]. The…”

“…A useful tool to characterize the IP3 receptor is heparin. It inhibits binding of IP3 to its receptor [5][6][7] and IP3 induced cl+ release [8][9][10]. The isolation of the IP3 receptor on heparin agarose and its incorporation into lipid vesicles led to the conclusion that the IP3 receptor itself fonns the Ca 2 + channel [11].…”