RAPID ALDOSTERONE-INDUCED CELL-VOLUME INCREASE OF ENDOTHELIAL-CELLS MEASURED BY THE ATOMIC-FORCE MICROSCOPE

Atomic force microscopy (AFM) is a useful technique for imaging the su rface of living cells in three dimensions. The authors applied AFM to obtain morphological information of individual cultured endothelial ce lls of bovine aorta under stationary and strain conditions and to simu ltaneously measure changes in cell volume in response to aldosterone. This mineralocorticoid hormone is known to have acute, non-genomic eff ects on intracellular pH, intracellular electrolytes and inositol-1,4, 5-triphosphate production. In this study whether endothelial cells und er tension change their volume in response to aldosterone was tested. Such changes were already shown in human leukocytes measured by Coulte r counter. In contrast to leukocytes that are more or less spherical a nd live in suspension, endothelial cells exhibit a complex morphology and adhere to a substrate. Thus, measurements of discrete cell volume changes in endothelial cells under physiological condition is only fea sible with more sophisticated techniques. By using AFM we could precis ely measure the absolute cell volume of individual living endothelial cells. Before the addition of aldosterone the cell volume of mechanica lly stressed endothelial cells mimicking arterial blood pressure was 1 827 +/- 172 fl. Cell volume was found to increase by 28% 5 min after h ormone exposure. Twenty-five minutes later cell volume was back to nor mal despite the continuous presence of aldosterone in the medium. Amil oride, a blocker of the plasma membrane Na+/H+ exchanger prevented the initial aldosterone-induced volume increase. Taken together, AFM disc losed a transient swelling of endothelial cells induced by the activat ion of an aldosterone sensitive plasma membrane Na+/H+ exchanger. (C) 1997 Academic Press.