PT  - JOURNAL ARTICLE
AU  - F Nicoletti
AU  - V Bruno
AU  - S Cavallaro
AU  - A Copani
AU  - M A Sortino
AU  - P L Canonico
TI  - Specific binding sites for inositolhexakisphosphate in brain and anterior pituitary.
DP  - 1990 May 01
TA  - Molecular Pharmacology
PG  - 689--693
VI  - 37
IP  - 5
4099  - http://molpharm.aspetjournals.org/content/37/5/689.short
4100  - http://molpharm.aspetjournals.org/content/37/5/689.full
SO  - Mol Pharmacol1990 May 01; 37
AB  - [3H]Inositolhexakisphosphate (InsP6) binds to a single population of specific and saturable recognition sites in membranes prepared from cerebral hemispheres, anterior pituitaries, or cultured cerebellar neurons. Binding is temperature and pH dependent, exhibits slow association and dissociation kinetics, and differentiates among various inositolpolyphosphates (InsP6 is much more potent than inositol-1,3,4,5,6-pentakis- and inositol-1,3,4,5-tetrakisphosphate, whereas inositol-1,4,5-trisphosphate is inactive as a displacer). In membranes from cerebral hemispheres, saturation analysis reveals a KD value of 33 +/- 4 nM and a maximal density (Bmax) of 152 +/- 23 pmol/mg of protein. Both affinity and density of [3H]InsP6 binding are lower in membranes from anterior pituitaries. In cultured cerebellar neurons, micromolar concentrations of divalent cations enhance both [3H]InsP6 binding and InsP6-stimulated 45Ca2+ uptake, suggesting that activation of specific receptors may be involved in the stimulation of 45Ca2+ uptake produced by InsP6. These data support the recent view that InsP6, as other inositolpolyphosphates, may act as a signal molecule in excitable cells.