Electrophysiological Responses to Angiotensin II of Isolated Rat Adrenal Glomerulosa Cells*

Publisher Website
Google Scholar
Abstract
The membrane response of isolated rat glomerulosa cells to the application of angiotensin II (A II) has been studied using intracellular voltage measurements. The membrane response is biphasic. The first, brief phase involves an increase in membrane conductance and a hyperpolarization from the resting membrane potential. The second, long-lasting phase is characterized by a large decrease in membrane conductance and a depolarization from the resting membrane potential. The reversal potential for the second phase is -94 .+-. 1.2 mV, and a linear relationship between reversal potential and external K+ indicates that the A II-mediated response is predominantly inhibition of K+ permeability. The A II response can be elicited when external Ca2+ is replaced by Sr2+ or Ba2+, but the response is inhibited when Mn2+ is added to the bath or when stimulated in a Ca2+-free solution. A II appears to inhibit at least two conductances, when the cell is stimulated by long current steps. External application of A II Inhibited the Ca2+ regenerative response found in glomerulosa cells in a dose-dependent manner. The rate of rise of the regenerative response was greatly attenuated by A II; half-maximal inhibition was produced by about 10-9 M A II. In addition, rectification, evident at voltages more positive than -60 mV during current stimulation, was also inhibited. In conclusion, A II causes rat glomerulosa cells to depolarize due to the inhibition of resting K+ permeability. Action potential activity is not observed during A II-mediated membrane depolarization; rather, both Ca2+ and K+ conductances appear to be inhibited during A II application.