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Uptake of meta-iodobenzylguanidine by bovine chromaffin granule membranes

Journal Article · · Mol. Pharmacol.; (United States)
OSTI ID:5527937
meta-Iodobenzylguanidine, an adrenal imaging agent used for the scintigraphic detection of human pheochromocytoma, is a substrate for the monoamine uptake system of chromaffin granules. It is accumulated by bovine chromaffin granule membrane vesicles in the presence of ATP, and it can be released by an osmotic shock. The uptake is dependent upon the generation of an H+-electrochemical gradient by an ATP-dependent H+ pump since it is blocked by an H+ ionophore and since meta-iodobenzylguanidine uptake can be driven by imposing an artificial pH gradient (inside acidic) on the membrane vesicles. The transport is saturable and its Km value (2.0 microM at pH 8.0) is similar to that of noradrenaline (5.3 microM). Transport occurs through the monoamine transporter since it is blocked by the same inhibitors, tetrabenazine and reserpine, and also by the transporter substrates noradrenaline and serotonin. Noradrenaline inhibits meta-iodobenzylguanidine uptake competitively (Ki = 13 microM). In addition, meta-iodobenzylguanidine displaces dihydrotetrabenazine and reserpine from their binding sites on chromaffin granule membranes. It is thus likely that, after in vivo administration, (131I) meta-iodobenzylguanidine is ultimately stored in chromaffin granules and that it is translocated by the monoamine transporter.
Research Organization:
Institut de Biologie Physico-Chimique, Paris, France
OSTI ID:
5527937
Journal Information:
Mol. Pharmacol.; (United States), Journal Name: Mol. Pharmacol.; (United States) Vol. 3; ISSN MOPMA
Country of Publication:
United States
Language:
English

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