Sparsentan is viewed as a dual antagonist of
endothelin type A (ETA) receptor and
angiotensin II (AngII) receptor and it could be beneficial in patients with
focal segmental glomerulosclerosis. Moreover, it could improve glomerular filtration rate and augment protective tissue remodeling in mouse models of
focal segmental glomerulosclerosis. The ionic mechanisms through which it interacts with the magnitude and/or gating kinetics of ionic currents in excitable cells were not thoroughly investigated. Herein, we aimed to examine the effects of varying
sparsentan concentrations on ionic currents residing in pituitary GH3 somatolactotrophs. From whole-cell current recordings made in GH3 cells,
sparsentan (0.3-100 μM) differentially inhibited the peak and late components of voltage-gated Na+ current (INa). The IC50 value of
sparsentan required to exert a reduction in peak and late INa in GH3 cells was 15.04 and 1.21 μM, respectively; meanwhile, the KD value estimated from its shortening in the slow component of INa inactivation time constant was 2.09 μM. The
sparsentan (10 μM) presence did not change the overall current-voltage relationship of INa; however, the steady-state inactivation curve of the current was shifted to more negative potential in its presence (10 μM), with no change in the gating charge of the curve. The window INa activated by a brief upsloping ramp was decreased during exposure to
sparsentan (10 μM); moreover, recovery of peak INa became slowed in its presence. The
Tefluthrin (Tef)-stimulated resurgent INa activated in response to abrupt depolarization followed by the descending ramp pulse was additionally attenuated by subsequent application of
sparsentan. In continued presence of Tef (3 μM) or β-pompilidotoxin (3 μM), further application of
sparsentan (3 μM) reversed their stimulation of INa. However,
sparsentan-induced inhibition of INa failed to be overcome by subsequent application of either
endothelin 1 (1 μM) or
angiotensin II (1 μM); moreover, in continued presence of
endothelin (1 μM) or
angiotensin II (1 μM), further addition of
sparsentan (3 μM) effectively decreased peak INa. Additionally, the application of
sparsentan (3 μM) inhibited the peak and late components of erg-mediated K+ current in GH3 cells, although it mildly decreased the amplitude of delayed-rectifier K+ current. Altogether, this study provides a distinct yet unidentified finding that
sparsentan may perturb the amplitude or gating of varying ionic currents in excitable cells.