Rapid formation of inositol 1,3,4,5-tetrakisphosphate and inositol 1,3,4-trisphosphate in rat parotid glands may both result indirectly from receptor-stimulated release of inositol 1,4,5-trisphosphate from phosphatidylinositol 4,5-bisphosphate
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Overview
Ex vivo study demonstrates carbachol-stimulated synthesis of inositol tetrakisphosphate from inositol trisphosphate in rat parotid tissue, indicating dual metabolic pathways for inositol signaling.
Key Points
- To investigate the enzymatic pathways and kinetics governing the formation and metabolism of inositol 1,3,4,5-tetrakisphosphate and inositol 1,3,4-trisphosphate upon receptor stimulation in rat parotid glands.
- Stimulated [3H]inositol-labelled rat parotid slices with 1 mM carbachol, assessing kinetics and turnover with atropine blockade.
- Assayed parotid homogenates for ATP-dependent kinase and phosphatase activities using radiolabelled inositol phosphate intermediates.
- Carbachol stimulated rapid formation of [3H]inositol 1,3,4,5-tetrakisphosphate, peaking at 20 seconds before declining to a new steady state, exhibiting a slower initial formation rate than inositol 1,4,5-trisphosphate.
- Parotid homogenates synthesized inositol tetrakisphosphate from inositol 1,4,5-trisphosphate in an ATP-dependent manner and specifically dephosphorylated inositol 1,3,4,5-tetrakisphosphate to inositol 1,3,4-trisphosphate.
Cite This Study
Hawkins et al. (1986) studied this question.