Phosphoinositide metabolism in intestinal smooth muscle: preferential production of Ins(1,4,5)P3 in circular muscle cells. 1991

K S Murthy, and G M Makhlouf
Department of Medicine, Medical College of Virginia, Richmond 23298-0711.

The pattern of inositol phospholipid metabolism in response to stimulation by contractile agonists was examined in muscle cells isolated separately from circular and longitudinal muscle layers of guinea pig intestine. Addition of cholecystokinin octapeptide (CCK-8) to circular muscle cells caused a prompt decrease in phosphatidylinositol 4,5-bisphosphate (PtdInsP2) (50 +/- 6%) and PtdInsP (38 +/- 9%), which reached a nadir in 15 s. Addition of CCK-8 to longitudinal muscle cells caused a decrease in PtdInsP only (42 +/- 6%); PtdInsP2 levels, which were three times lower in this cell type, did not change throughout the period of stimulation. Hydrolysis of PtdInsP2 in circular muscle cells was accompanied by a concentration-dependent increase in inositol 1,4,5-trisphosphate [Ins(1,4,5)P3]; the maximal increase was 10 to 16 times greater in circular muscle cells as measured by radioreceptor assay and by ion-exchange chromatography. The small amounts of InsP3 produced in longitudinal muscle cells did not result from more rapid degradation, since the rates of disappearance of exogenous Ins(1,4,5)P3 in both cell types were similar. Within 5 s after addition of CCK-8, InsP3 comprised 73 +/- 5% of total inositol phosphates produced in circular muscle cells and 2.0 +/- 0.2% in longitudinal muscle cells. These divergent patterns indicate that inositol phospholipid metabolism is channeled toward generation of InsP3 in circular muscle cells only; the metabolic pattern in these cells parallels the selective presence of high-affinity InsP3 receptors and the pattern of intracellular Ca2+ mobilization.

UI MeSH Term Description Entries
D007295 Inositol Phosphates Phosphoric acid esters of inositol. They include mono- and polyphosphoric acid esters, with the exception of inositol hexaphosphate which is PHYTIC ACID. Inositol Phosphate,Phosphate, Inositol,Phosphates, Inositol
D007413 Intestinal Mucosa Lining of the INTESTINES, consisting of an inner EPITHELIUM, a middle LAMINA PROPRIA, and an outer MUSCULARIS MUCOSAE. In the SMALL INTESTINE, the mucosa is characterized by a series of folds and abundance of absorptive cells (ENTEROCYTES) with MICROVILLI. Intestinal Epithelium,Intestinal Glands,Epithelium, Intestinal,Gland, Intestinal,Glands, Intestinal,Intestinal Gland,Mucosa, Intestinal
D007700 Kinetics The rate dynamics in chemical or physical systems.
D009130 Muscle, Smooth Unstriated and unstriped muscle, one of the muscles of the internal organs, blood vessels, hair follicles, etc. Contractile elements are elongated, usually spindle-shaped cells with centrally located nuclei. Smooth muscle fibers are bound together into sheets or bundles by reticular fibers and frequently elastic nets are also abundant. (From Stedman, 25th ed) Muscle, Involuntary,Smooth Muscle,Involuntary Muscle,Involuntary Muscles,Muscles, Involuntary,Muscles, Smooth,Smooth Muscles
D011956 Receptors, Cell Surface Cell surface proteins that bind signalling molecules external to the cell with high affinity and convert this extracellular event into one or more intracellular signals that alter the behavior of the target cell (From Alberts, Molecular Biology of the Cell, 2nd ed, pp693-5). Cell surface receptors, unlike enzymes, do not chemically alter their ligands. Cell Surface Receptor,Cell Surface Receptors,Hormone Receptors, Cell Surface,Receptors, Endogenous Substances,Cell Surface Hormone Receptors,Endogenous Substances Receptors,Receptor, Cell Surface,Surface Receptor, Cell
D002463 Cell Membrane Permeability A quality of cell membranes which permits the passage of solvents and solutes into and out of cells. Permeability, Cell Membrane
D006168 Guinea Pigs A common name used for the genus Cavia. The most common species is Cavia porcellus which is the domesticated guinea pig used for pets and biomedical research. Cavia,Cavia porcellus,Guinea Pig,Pig, Guinea,Pigs, Guinea
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D012503 Saponins A type of glycoside widely distributed in plants. Each consists of a sapogenin as the aglycone moiety, and a sugar. The sapogenin may be a steroid or a triterpene and the sugar may be glucose, galactose, a pentose, or a methylpentose. Saponin
D015544 Inositol 1,4,5-Trisphosphate Intracellular messenger formed by the action of phospholipase C on phosphatidylinositol 4,5-bisphosphate, which is one of the phospholipids that make up the cell membrane. Inositol 1,4,5-trisphosphate is released into the cytoplasm where it releases calcium ions from internal stores within the cell's endoplasmic reticulum. These calcium ions stimulate the activity of B kinase or calmodulin. 1,4,5-InsP3,Inositol 1,4,5-Triphosphate,Myo-Inositol 1,4,5-Trisphosphate,1,4,5-IP3,Myoinositol 1,4,5-Triphosphate

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