Probenecid Inhibits Platelet Responses to Aggregating Agents in Vitro and Has a Synergistic Inhibitory Effect with Penicillin G

Abstract

SummaryProbenecid is an anion channel blocker and uricosuric agent, originally developed to slow the rate of excretion of penicillin. It is now also administered with many other drugs to reduce their required dosages. Recently, probenecid (2.5 mM) has been used to prevent leakage of fura-2 or fluo-3 when these indicators of cytosolic Ca2+ levels have been introduced into cells. However, we found that probenecid markedly inhibited the increases in cytosolic Ca2+ caused by ADP, thrombin, the thrombin receptor-activating peptide (SFLLRN, TRAP), ADP, sodium arachidonate, the thromboxane A2 (TXA2) mimetic U46619, and platelet-activating factor (PAF). This finding precluded the use of probenecid with platelets in measurements of cytosolic Ca2+ with indicators such as fura-2. We then investigated the effects of probenecid on aggregation and release of 14C-serotonin from prelabeled platelets. Responses to all the agonists were inhibited by 2.5 mM probenecid, but concentrations as low as 0.25-0.5 mM inhibited responses to agonists that act largely via TXA2 (collagen, sodium arachidonate and U46619). Collagen-induced TXA2 formation was inhibited in a dose-dependent manner. Responses of aspirin-pretreated platelets to thrombin, SFLLRN, U46619 and PAF were also inhibited by probenecid, indicating that prevention of TXA2 formation does not account for all the inhibitory effects. The combination of probenecid with penicillin G produced additive or synergistic inhibition of platelet responses; responses dependent on TXA2 were synergistically inhibited by concentrations of the drugs that are reached in vivo. The synergistic inhibitory effect of probenecid on platelet functions could further impair hemostasis if it has already been partially compromised by the administration of other drugs.

Spatiotemporal calcium signaling in a Drosophila melanogaster cell line stably expressing a Drosophila muscarinic acetylcholine receptor

“…Our findings based on digital imaging microscopy show that the anion transport inhibitor, probenecid, offers an approach to overcoming this particular limitation by reducing leakage and providing a more homogeneous intracellular dye distribution. While studies have indicated additional cellular effects with probenecid, such as oxidative-phosphorylation uncoupling in mitochondria (Masereeuw et al 2000) and inhibitory effects on platelet release-inducing agents (Packham et al 1996), at the concentration used in the present study (1 mM) no significant effect was observed on either basal [Ca 2+ ] i , mAChR-activated [Ca 2+ ] i increase, or CCE. Should probenecid stimulate membrane depolarization in S2-DM1 cells it would not be expected to result in a basal [Ca 2+ ] i increase as was observed with neuronal cell lines (DiVirgilio et al 1988) given the apparent lack of voltage-gated Ca 2+ channels in S2 cells.…”

Dependence of Platelet Thrombus Stability on Sustained Glycoprotein IIb/IIIa Activation Through Adenosine 5′-Diphosphate Receptor Stimulation and Cyclic Calcium Signaling

“…The washed cells were resuspended in homologous PPP containing Argatroban (100 mol/l) at a 40% hematocrit. Unlike previously suggested (21) but in agreement with recent reports (22), we did not use probenecid to prevent the leakage of fluo-3 because of its effects on platelet function (23). The [Ca 2ϩ ] i of 10 randomly selected platelets incorporated at different positions within a thrombus was measured using confocal microscopy.…”

Thrombocytopenia from Combination Treatment with Oseltamivir and Probenecid: Case Report, MedWatch Data Summary, and Review of the Literature

“…7 We also identified articles describing probenecid effects on decreasing platelet aggregation. 8,9 Package inserts for each drug did not list thrombocytopenia or decreased platelet counts as adverse effects. 10,11 Using a commercially available search tool (http://www.cerner.com/public/Cerner_3.asp?id= 28747), we also evaluated data from the FDA's AERS through the first quarter of 2008.…”