Phenamil, an amiloride analogue, inhibits differentiation of Friend murine erythroleukemic cells.
Amiloride has been reported to inhibit Friend murine erythroleukemic (MEL) cell commitment to differentiate by inhibiting the MEL cell plasma membrane Na+-Ca2+ antiporter (R. L. Smith, I. G. Macara, R. Levenson, D. Housman, and L. Cantley. J. Biol. Chem. 257: 773-780, 1982). We therefore screened a series of amiloride analogues to determine whether a more potent and specific inhibitor of MEL cell differentiation could be found. In our experiments, as in those of Lubin (J. Cell. Physiol. 124: 539-544, 1985), amiloride itself did not inhibit MEL cell differentiation. However, we did find that the amiloride analogue phenamil reversibly inhibits dimethyl sulfoxide (DMSO)-induced MEL cell commitment to differentiate with a K1/2 of 2.5-5.0 microM (in plasma clot assay). At an extracellular concentration of 15 microM, phenamil inhibits commitment to differentiate by approximately 90% in the plasma clot assay while having a minimal effect on growth. Phenamil is not metabolized but is rapidly taken up by MEL cells. Phenamil was most effective as an inhibitor when present during the first 12 h of DMSO treatment, indicating that phenamil affects the early commitment process rather than later steps involved in hemoglobin synthesis. Phenamil does not, however, inhibit the early differentiation-induced decrease in [Na+]i and the concomitant drop in the Na+-K+ pump rate. A specific binding site for phenamil is suggested because some analogues in which the phenamil structure is slightly modified are unable to inhibit differentiation.
Lannigan
D A
DA
Department of Biophysics, University of Rochester, School of Medicine and Dentistry, New York 14642.
Bennington
J B
JB
Cragoe
E J
EJ
Knauf
P A
PA
D000584:Amiloride / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D005622:Friend murine leukemia virus; D004915:Leukemia, Erythroblastic, Acute / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D009994:Osmolar Concentration; D010042:Ouabain / Q000494:pharmacology; D012413:Rubidium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism
C047088:phenylamil; D010042:Ouabain; D000584:Amiloride; D012964:Sodium; D012413:Rubidium; D004121:Dimethyl Sulfoxide