Riquelme G, Jaimovich E, Lingsch C, Behn C. Lipid monolayer expansion by calcium-chlorotetracycline at the air/water interface and, as inferred from cell shape changes, in the human erythrocyte membrane.
BIOCHIMICA ET BIOPHYSICA ACTA 1982;
689:219-29. [PMID:
7115708 DOI:
10.1016/0005-2736(82)90254-1]
[Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Chemically induced shape changes of the human erythrocyte may result from cell membrane bending by surface tension changes at the lipid bilayer (Evans. E.A. (1974( Biophys. J. 14, 923-931) implicating differential expansion of the monolayers coupled to form the red cell membrane (Sheetz, M.P. and Singer, S.J. (1974) Proc. Natl. Acad. Sci. U.S.A. 71, 4457-4461). Interacting with calcium, the antibiotic chlorotetracycline (CTC) transforms crenated cells (echinocytes) into cup-shaped ones (stomatocytes), presumably expanding thereby the red cell membrane inner leaflet relative to the outer one (Behn, C., Lübbemeier, A. and Weskamp, P. (1977) Pflügers Arch. 372, 259-268). Whether the Ca-CTC interaction with lipid monolayers may in fact expand the latter, has now been examined by surface tension measurements at the air/water interface. CTC and lipids appeared to compete for the available sites at the air/water interface, contributing additively to its surface pressure. Ca increased both the adsorption rate of the antibiotic to the interface and the CTC-induced surface pressure increment. The latter was not influenced by the subphase pH and ionic strength, or by the type of phospholipid polar head. Correspondingly, CTC-induced cell shape changes should be determined by the pCa values facing either monolayer of the erythrocyte membrane. Both stomatocytes and echinocytes could indeed by obtained with 0.5 mmol . 1(-1) CTC, the cell shape depending on whether the external medium was adjusted respectively to pCa 9 or to pCa 3. Fluorescence microscopy revealed the Ca-CTC complex to be mostly restricted to the cell in stomatocytes and to the external medium in echinocytes. The possibility of inducing alternative cell shapes by varying the transmembrane Ca-CTC distribution, and the demonstration of a Ca-dependent expansion of even relatively compressed lipid monolayers by CTC, together suggest that the Ca-CTC complex may also differentially expand either leaflet of the red cell membrane.
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