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Picomolar platelet-activating factor mobilizes Ca to change platelet shape without activating phospholipase C or protein kinase C; simultaneous fluorometric measurement of intracellular free Ca concentration and aggregation.
J Pharmacol Exp Ther. 1994 Nov; 271(2):824-31.JP

Abstract

The purpose of this study was to investigate signal transduction mechanisms activated by low and high concentrations of platelet-activating factor (PAF) in rabbit platelets and to contrast the responses to those induced by thrombin. We measured changes in intracellular free calcium ([Ca++]i) with fura2, while monitoring light scatter simultaneously as a measure of shape change and aggregation in a dual-excitation dual-emission spectrofluorometer. An abrupt 20% fall in light scatter, coincident with the peak of the [Ca++]i, indicated shape change in Ca-containing or Ca-free medium and was blocked by BAPTA loading and 10 microM cytochalasin B. A secondary decline in light scatter, indicating aggregation, occurred only in Ca-containing medium and only under conditions favoring protein kinase C (PKC) activation. PAF at 10(-12) M did not increase 1,4,5-inositol triphosphate content, which suggested PKC would not be activated. However, PAF at 10(-12) rapidly increased [Ca++]i to 900 nM in 7 sec seemingly by Ca influx through receptor-operated channels inducing shape change. PAF at 10(-9) and 10(-8) M increased [Ca++]i to 2 microM in 12 sec and induced both shape change and aggregation. However, in platelets pretreated with 100 nM staurosporine to inhibit protein kinases, 10(-9) M PAF did not cause aggregation even though [Ca++]i still rose to 2 microM, which indicated that PKC plays a role in aggregation but not in Ca++ mobilization.(

ABSTRACT

TRUNCATED AT 250 WORDS)

Authors+Show Affiliations

Department of Pharmacology, School of Medicine, University of Missouri, Columbia.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

7965802

Citation

James-Kracke, M R., et al. "Picomolar Platelet-activating Factor Mobilizes Ca to Change Platelet Shape Without Activating Phospholipase C or Protein Kinase C; Simultaneous Fluorometric Measurement of Intracellular Free Ca Concentration and Aggregation." The Journal of Pharmacology and Experimental Therapeutics, vol. 271, no. 2, 1994, pp. 824-31.
James-Kracke MR, Sexe RB, Shukla SD. Picomolar platelet-activating factor mobilizes Ca to change platelet shape without activating phospholipase C or protein kinase C; simultaneous fluorometric measurement of intracellular free Ca concentration and aggregation. J Pharmacol Exp Ther. 1994;271(2):824-31.
James-Kracke, M. R., Sexe, R. B., & Shukla, S. D. (1994). Picomolar platelet-activating factor mobilizes Ca to change platelet shape without activating phospholipase C or protein kinase C; simultaneous fluorometric measurement of intracellular free Ca concentration and aggregation. The Journal of Pharmacology and Experimental Therapeutics, 271(2), 824-31.
James-Kracke MR, Sexe RB, Shukla SD. Picomolar Platelet-activating Factor Mobilizes Ca to Change Platelet Shape Without Activating Phospholipase C or Protein Kinase C; Simultaneous Fluorometric Measurement of Intracellular Free Ca Concentration and Aggregation. J Pharmacol Exp Ther. 1994;271(2):824-31. PubMed PMID: 7965802.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Picomolar platelet-activating factor mobilizes Ca to change platelet shape without activating phospholipase C or protein kinase C; simultaneous fluorometric measurement of intracellular free Ca concentration and aggregation. AU - James-Kracke,M R, AU - Sexe,R B, AU - Shukla,S D, PY - 1994/11/1/pubmed PY - 1994/11/1/medline PY - 1994/11/1/entrez SP - 824 EP - 31 JF - The Journal of pharmacology and experimental therapeutics JO - J Pharmacol Exp Ther VL - 271 IS - 2 N2 - The purpose of this study was to investigate signal transduction mechanisms activated by low and high concentrations of platelet-activating factor (PAF) in rabbit platelets and to contrast the responses to those induced by thrombin. We measured changes in intracellular free calcium ([Ca++]i) with fura2, while monitoring light scatter simultaneously as a measure of shape change and aggregation in a dual-excitation dual-emission spectrofluorometer. An abrupt 20% fall in light scatter, coincident with the peak of the [Ca++]i, indicated shape change in Ca-containing or Ca-free medium and was blocked by BAPTA loading and 10 microM cytochalasin B. A secondary decline in light scatter, indicating aggregation, occurred only in Ca-containing medium and only under conditions favoring protein kinase C (PKC) activation. PAF at 10(-12) M did not increase 1,4,5-inositol triphosphate content, which suggested PKC would not be activated. However, PAF at 10(-12) rapidly increased [Ca++]i to 900 nM in 7 sec seemingly by Ca influx through receptor-operated channels inducing shape change. PAF at 10(-9) and 10(-8) M increased [Ca++]i to 2 microM in 12 sec and induced both shape change and aggregation. However, in platelets pretreated with 100 nM staurosporine to inhibit protein kinases, 10(-9) M PAF did not cause aggregation even though [Ca++]i still rose to 2 microM, which indicated that PKC plays a role in aggregation but not in Ca++ mobilization.(ABSTRACT TRUNCATED AT 250 WORDS) SN - 0022-3565 UR - https://www.unboundmedicine.com/medline/citation/7965802/Picomolar_platelet_activating_factor_mobilizes_Ca_to_change_platelet_shape_without_activating_phospholipase_C_or_protein_kinase_C L2 - https://jpet.aspetjournals.org/cgi/pmidlookup?view=long&pmid=7965802 DB - PRIME DP - Unbound Medicine ER -