ANG II blocks potassium currents in zona glomerulosa cells from rat, bovine, and human adrenals.
Angiotensin II (ANG II) is a principal secretagogue of adrenal zona glomerulosa (ZG) cells. The transduction process includes a depolarization of the plasma membrane and the activation of calcium influx. The ANG II-induced depolarization is associated with an increase in total membrane resistance. To directly address the mechanism underlying these observations, we examined the effect of ANG II on K+ currents of rat, bovine, and human ZG cells, using whole cell patch clamp. Although some differences were seen in the characteristics of K+ currents between species, ANG II consistently blocked outward currents in ZG cells [rat: 47.1 +/- 4.5% (SE), n = 17; bovine: 38.6 +/- 3.3%, n = 21; and human: 13-63%, n = 3]. With the use of the cell-attached mode, single-channel recordings in bovine ZG cells demonstrated K+ channels that were reversibly blocked when ANG II was added to the bath solution. This indicates that the block of K+ channels by ANG II involves a diffusible intracellular messenger rather than a direct receptor-channel interaction. The decreased conductance of K+ can account for the ANG II-induced membrane depolarization.
Brauneis
U
U
Department of Physiology, Boston University School of Medicine 02118.
Vassilev
P M
PM
Quinn
S J
SJ
Williams
G H
GH
Tillotson
D L
DL
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D002417:Cattle; D004594:Electrophysiology / Q000379:methods; D006801:Humans; D066298:In Vitro Techniques; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D013045:Species Specificity; D013997:Time Factors; D015384:Zona Glomerulosa / Q000502:physiology*
D015221:Potassium Channels; D000804:Angiotensin II