Dipyridamole stimulates types II cAMP-dependent protein kinase in vitro

It has been hypothesized that, in addition to freezing injury, some damage to platelets may result from the cell packing that occurs during removal of the cryoprotectant. This study examined DMSO removal by fluid exchange across hollow-fiber (HF) filters as an alternative to centrifugation. The DMSO solution with or without cell suspension was passed once through the filter. The optimum exchange during unloading of DMSO was determined by varying the flow rates in the external and internal compartments of the HF filter. Initially, buffered solutions of a 5% DMSO solution in the absence of platelets were pumped into the fibers and exchanged against PBS. The residual DMSO was determined by osmometry. The exchange of DMSO across the membrane was flow dependent and also influenced by the chemical nature of the HF fibers. No protocol using a reasonable rate flow through the fibers removed more than 95% of the DMSO in a single pass. The optimum protocol was achieved with polysynthane fibers with an internal flow rate of approximately 20 mi/min and an external flow rate of 100 ml/min. Subsequently, frozen/thawed platelet concentrates in DMSO were washed using centrifugation and compared to the HF filtration method. Platelet quality was assayed by flow cytometry, cell count, morphology and osmotic stress test. Both filtration and centrifugal washing techniques resulted in comparable morphological scores and numbers of discoid cells. When agents reducing platelet activation were added, platelet quality was improved after washing by either technique. The lower platelet osmotic response with HF filtration than with centrifugation while using activation inhibitors was attributed to the remaining amount of the inhibitors. All other parameters tested were similar. The expression of CD62P was equivalent with both techniques, and centrifugation did not activate platelets more than filtration contrary to what was originally anticipated. In conclusion, platelet quality was comparable after washing by either technique but hollow fiber filtration does remove cryoprotectant more rapidly than does centrifugation.

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Stimulation of Long-Chain Fatty Acid Uptake by Dipyridamole in Isolated Myocytes

Abdel-aleem

Elguindy

Sallam

et al. 1999

Journal of Cardiovascular Pharmacology

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This study was designed to investigate the effects of the cardiovascular drug dipyridamole on fatty acid metabolism in isolated cardiac myocytes. Effects of dipyridamole on the oxidation of long-chain (palmitate) fatty acid, medium-chain (octanoate) fatty acid, and the carbohydrate intermediate (pyruvate) were determined by using isolated cardiac myocytes from both normal and diabetic rats. Dipyridamole increased palmitate oxidation in a concentration-dependent manner in both normal and diabetic myocytes. Maximal stimulation of palmitate oxidation (175% of control) was observed with 100 microM dipyridamole. In contrast, oxidation of octanoate and pyruvate was not affected. The stimulation of palmitate oxidation by dipyridamole persisted despite its removal from the incubation medium. In contrast to the effect in myocytes, palmitate oxidation was not affected by dipyridamole in isolated rat heart mitochondria. Palmitate uptake was increased by 2.5- and 1.6-fold when palmitate concentration was adjusted to 0.05 and 0.2 mM, respectively. Dipyridamole did not affect lipolysis in isolated myocytes. When dipyridamole (100 microM) and L-carnitine (5 mM) were added together to the incubation medium, palmitate oxidation was further increased to 223% of the control. The nucleoside transport inhibitor nitrobenzylthioinosine (NBMPR) failed to increase palmitate oxidation in isolated myocytes. Although palmitate oxidation in diabetic cells is much higher than that in normal myocytes, dipyridamole increased palmitate oxidation by 243% in diabetic myocytes over its baseline oxidation rate in normal cells. These results suggest that increased palmitate oxidation in isolated cardiac myocytes after dipyridamole administration occurs independent of effects on either the phosphodiesterase enzyme or nucleoside transport protein, but it may result from increased palmitate transport across the plasma membrane.

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Dipyridamole stimulates types II cAMP-dependent protein kinase in vitro

Cited by 3 publications

References 30 publications

Isobutylmethylxanthine and other classical cyclic nucleotide phosphodiesterase inhibitors affect cAMP-dependent protein kinase activity

Isobutylmethylxanthine and other classical cyclic nucleotide phosphodiesterase inhibitors affect cAMP-dependent protein kinase activity

Use of hollow fiber membrane filtration for the removal of DMSO from platelet concentrates

Stimulation of Long-Chain Fatty Acid Uptake by Dipyridamole in Isolated Myocytes

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