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Title: Epidermal growth factor (EGF)-stimulated inositol phosphate formation in hepatocytes is abolished by pertussis toxin and phorbol esters

The EGF-stimulated rise in intracellular Ca/sup 2 +/ (Ca/sup 2 +/)/sub i/ and Ca/sup 2 +/-dependent protein phosphorylation events in isolated hepatocytes are blocked by pertussis toxin and phorbol ester pretreatment. The present study characterized the EGF-stimulated formation of inositol 1,4,5-trisphosphate (Ins(1,4,5)P/sub 3/) and inositol 1,3,4-trisphosphate (Ins(1,3,4)P/sub 3/) in hepatocytes using HPLC methodology to separate the InsP/sub 3/ isomers. Both 66 nM EGF and 10 nM angiotensin II (ANG II) caused a rapid increase in the Ins(1,4,5)P/sub 3/ isomer although EGF-stimulated formation was smaller. At a concentration of ANG II (0.1 nM) which gave an equivalent rise in (Ca/sup 2 +/)/sub i/ as 66 nM EGF, the kinetics and magnitude of Ins(1,4,5)P/sub 3/ formation were similar. EGF or ANG II-stimulated formation of the Ins(1,3,4)P/sub 3/ isomer was more gradual and increased beyond the level of Ins(1,4,5)P/sub 3/ after 60 sec. The initial EGF and ANG II-stimulated increase in both InsP/sub 3/ isomers was not affected by removing external Ca/sup 2 +/ with a 10-fold excess of EGTA. Pretreatment of rats with pertussis toxin for 72 hrs blocked the ability of EGF to increase Ins(1,4,5)P/sub 3/ but did not affect the increase due to ANG II. Three main pretreatment of cellsmore » with 1 ..mu..g/ml phorbol 12-myristate-13-acetate (PMA) also inhibited the EGF-stimulated Ins(1,4,5)P/sub 3/ formation. PMA slightly attenuated Ins(1,4,5)P/sub 3/ formation stimulated by 0.1 nM ANG II but not enough to affect the Ca/sup 2 +/ signal. These data suggest that the signal transduction system used by EGF receptors to increase Ins (1,4,5)P/sub 3/ in hepatocytes is somehow different from that used by ANG II receptors.« less
Authors:
;
Publication Date:
OSTI Identifier:
6065829
Report Number(s):
CONF-870644-
Journal ID: CODEN: FEPRA
Resource Type:
Conference
Resource Relation:
Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States); Journal Volume: 46:6; Conference: 78. annual meeting of the American Society of Biological Chemists conference, Philadelphia, PA, USA, 7 Jun 1987
Research Org:
Univ. of Virginia School of Medicine, Charlottesville
Country of Publication:
United States
Language:
English
Subject:
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.; GROWTH FACTORS; BIOCHEMICAL REACTION KINETICS; RECEPTORS; PHORBOL ESTERS; BIOLOGICAL EFFECTS; PHOSPHATES; BIOSYNTHESIS; TOXINS; ANGIOTENSIN; CALCIUM COMPOUNDS; INOSITOL; ISOMERS; LIQUID COLUMN CHROMATOGRAPHY; LIVER CELLS; PHOSPHORYLATION; RATS; ALKALINE EARTH METAL COMPOUNDS; ANIMAL CELLS; ANIMALS; ANTIGENS; CARBOHYDRATES; CARCINOGENS; CARDIOVASCULAR AGENTS; CHEMICAL REACTIONS; CHROMATOGRAPHY; DRUGS; ESTERS; GLOBULINS; INOSITOLS; KINETICS; MAMMALS; MATERIALS; MEMBRANE PROTEINS; MITOGENS; MONOSACCHARIDES; ORGANIC COMPOUNDS; OXYGEN COMPOUNDS; PHOSPHORUS COMPOUNDS; PROTEINS; REACTION KINETICS; RODENTS; SACCHARIDES; SEPARATION PROCESSES; SOMATIC CELLS; SYNTHESIS; TOXIC MATERIALS; VASOCONSTRICTORS; VERTEBRATES 560300* -- Chemicals Metabolism & Toxicology