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Willis, John S. Xu, Wan Yan 2011-05-07T13:06:51Z 2011-05-07T13:06:51Z 10000-01-01 1993 In hamster red cells, amiloride-sensitive Na influx, 0.8 mmol/l cell/hr, is the only, carrier-mediated, Mg-dependent pathway for inward Na transport. This Na-dependent Mg transport is involved in the regulation of intracellular Mg$\sp{2+}$ concentration under physiological conditions. The Na-Mg transport system was studied in hamster red cells by unidirectional Na fluxes, as well as by net Mg movement. This amiloride-sensitive Na influx can be greatly stimulated by intracellular Mg$\sp{2+}$. Kinetic studies of both Na influx and Mg efflux in parallel show that a cooperative mechanism is involved in the activation by Mg$\sb{\rm i}$ with a Mg$\sb{0.5}$ of 1.7-1.8 mM and a Hill coefficient of 1.7-1.8 and that activation by Na$\sb{\rm o}$ fits a simple Michaelis-Menten equation, with a K$\sb{\rm m}$ of 83-104 mM. The similarity of the kinetics for Na and Mg activation and for amiloride inhibition (IC$\sb{50}$ = 0.3 mM) for both Na influx and net Mg loss confirm that transport of Mg$\sp{2+}$ is coupled with Na$\sp+$ with a ratio of 2 Na:1 Mg. Amiloride-sensitive Na influx is rapidly activated by hypotonic incubation in both fresh and Mg-loaded cells. Amiloride-sensitive Na influx requires ATP. Kinase promoters, phorbol ester and dibutyl cAMP, and phosphatase inhibitors, vanadate and okadaic acid, did not stimulate amiloride-sensitive Na influx. There was virtually no amiloride-sensitive Na efflux in hamster red cells with high (Na$\sp+$) $\sb{\rm i}$ and (Mg$\sp{2+}$) $\sb{\rm o}$, nor with hypotonicity, nor with ATP depletion. The ATP-dependence, asymmetry of Na transport, volume dependence and apparent lack of dependence on phosphorylation mechanisms all suggest that the Na-Mg transport mechanism in hamster red cells is not a simple carrier. Made available in DSpace on 2011-05-07T13:06:51Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9411831.pdf: 5054278 bytes, checksum: 191748814d8c5556e2caca686664c857 (MD5) Previous issue date: 1993 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:50:21Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:22:59-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission ETDs are only available to UIUC Users without author permission U of I Only AAI9411831 (UMI)AAI9411831 http://hdl.handle.net/2142/21375 eng Copyright 1993 Xu, Wan Yan Biology, Cell Biology, Animal Physiology Biology, Zoology Characteristics of sodium transport through the amiloride-sensitive sodium-magnesium pathway in hamster red cells text Molecular and Integrative Physiology Physiology University of Illinois at Urbana-Champaign Dissertation Ph.D.