Phorbol ester stimulates calcium sequestration in saponized human platelets

Journal Article · Wed Nov 25 04:00:00 EST 1987 · J. Biol. Chem.; (United States)

OSTI ID:5649452

Yoshida, K; Nachmias, V T

When platelets are activated by agonists, calcium (Ca2+) is released from an intracellular storage site. Recent studies using fura-2 show that, after thrombin stimulation, the rise in free calcium is transient and returns to base-line levels in 2-3 min, while the transient following ADP stimulation lasts only 15-20 s. We reported previously that the phorbol ester 12,13-phorbol myristate acetate (PMA), added at nanomolar levels after thrombin, immediately accelerated the rate of return of calcium to the base line severalfold. In the present study, we used both intact and saponized platelets to determine whether this is due to stimulation of calcium sequestration. Using fura-2 and intact platelets, we found 1) that PMA stimulated the restoration of free Ca2+ levels after ADP as well as after thrombin, and 2) that H-7, an inhibitor of protein kinase C (Ca2+/phospholipid-dependent enzyme), slowed the return of Ca2+ to baseline levels. Using saponized platelets, we also found 3) that pretreatment of platelets with PMA before saponin treatment increased the ATP-dependent /sup 45/Ca2+ uptake 2-fold, with a half-maximal effect at 5 nm; 4) that most of the Ca2+ released by ionomycin or by myoinositol 1,4,5-trisphosphate; and 5) that a GTP-binding protein inhibitor, guanosine 5'-O-(2-thiodiphosphate), decreased basal or PMA-stimulated /sup 45/Ca2+ uptake in saponin-treated platelets. Our data suggest that activation of protein kinase C stimulates the sequestration of Ca2+ independently of cAMP or myoinositol 1,4,5-trisphosphate.

• Research Organization: Univ. of Pennsylvania School of Medicine, Philadelphia
• OSTI ID: 5649452
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 262:33; ISSN JBCHA
• Country of Publication: United States
• Language: English

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550201 -- Biochemistry-- Tracer Techniques
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59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ADP
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METALS
AZINES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOLOGICAL EFFECTS
BIOLOGICAL MATERIALS
BLOOD
BLOOD CELLS
BLOOD PLATELETS
BODY FLUIDS
CALCIUM
CALCIUM 45
CALCIUM ISOTOPES
CARCINOGENS
CHELATING AGENTS
COAGULANTS
DAYS LIVING RADIOISOTOPES
DRUGS
ELEMENTS
ENZYME ACTIVITY
ENZYME INHIBITORS
ENZYMES
ESTERS
EVEN-ODD NUCLEI
HEMATOLOGIC AGENTS
HEMOSTATICS
HETEROCYCLIC COMPOUNDS
HYDROLASES
IN VITRO
INTERMEDIATE MASS NUCLEI
ISOTOPE APPLICATIONS
ISOTOPES
MATERIALS
MEMBRANE TRANSPORT
METALS
NUCLEI
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PEPTIDE HYDROLASES
PHORBOL ESTERS
PHOSPHORUS-GROUP TRANSFERASES
PHOSPHOTRANSFERASES
PIPERAZINES
PYRAZINES
RADIOISOTOPES
SERINE PROTEINASES
THROMBIN
TRACER TECHNIQUES
TRANSFERASES