| Abstract: |
The effects of gossypol on membrane functions of the human erythrocyte were studied. Gossypol (10 μM) had no effect on spontaneous hemolysis, osmotic fragility, cell volume, cholinesterase activity, hexose transport, ouabain-sensitive inorganic cation transport, ouabain-insensitive inorganic cation transport and nucleoside transport. Conversely, 10 μM gossypol inhibited inorganic anion transport by approximately 90% for three different substances, i.e., phosphate, sulfate and chloride. Inhibition of inorganic anion transport was specific as 10 μM gossypol had no effect on the eight aforementioned membrane-related functions of the human erythrocyte. Inhibition of inorganic anion transport was characterized using sulfate as the substrate and had the following features: 1) it was potent, with a K(i) of approximately 3 μM; 2) it was rapid, with onset occurring in <1 min; 3) it was potently blocked by physiological concentrations of albumin and plasma with 50% blocking achieved at 0.03% (w/v) albumin; 4) it occurred by a noncompetitive kinetic mechanism; 5) it was independent of medium Ca++, Mg++ or pH. Gossypol was bound to human erythrocytes and cell membranes isolated from erythrocytes. 4,4'Diisothiocyanostilbene-2,2'-disulfonic acid is a potent inhibitor of anion transport and can be covalently bound to band 3. Covalently bound 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid blocked a fraction of gossypol binding to erythrocyte membranes. This 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid-displaceable binding had the following characteristics: 1) it was saturable at approximately 10 μM gossypol; 2) it exhibited half-maximal binding at approximately 3 μM gossypol; 3) there were approximately 106 sites/cell, corresponding to the number of band 3 monomers per cell; 4) it comprised approximately 10% of the bound gossypol at an initial extracellular gossypol concentration of 10 μM; 5) it affected the conformation of approximately 30% of the membrane proteins corresponding to the fraction of band 3 in the erythrocyte membrane. The results demonstrated that gossypol, at low concentrations, is a specific, membrane-active agent. |
| Keywords: |
adult; human cell; drug efficacy; biology; in vitro study; physiology; drug receptor binding; diseases; biological transport; lipid bilayers; hydrogen-ion concentration; uridine; normal human; pharmacokinetics; in vitro; family planning; anions; gossypol; sulfates; erythrocyte membrane; 4,4' diisothiocyanatostilbene 2,2' disulfonic acid; 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid; anion exchange protein 1, erythrocyte; human; priority journal; osmosis; support, non-u.s. gov't; anion exchange; hematological effects; contraceptive agents, male; blood and hemopoietic system; contraception--men; contraceptive agents--side effects; examinations and diagnoses; gossypol--side effects; hemic system; laboratory examinations and diagnoses; laboratory procedures; 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid
|
