Lotshaw, David P.
M.S. (Master of Science)
Department of Biological Sciences
Adrenal glands; Aldosterone; Cell physiology
The present study identified a nonselective cation channel that may contribute to regulation of aldosterone secretion. Patch clamp experiments utilized isolated rat adrenal glomerulosa cells maintained less than 72 hours in primary culture. Recordings from cell-attached patches under near-physiological ionic conditions, 140 mM NaCl in the patch pipette, revealed the presence of spontaneous inward single-channel currents that exhibited a reversal potential of -12 mV and a linear slope conductance of 15+3 pS between 0 mV and -80 mV. The single-channel current-voltage relationship exhibited a decrease in slope conductance at membrane potentials more negative than -80 mV and inward rectification at membrane potentials more positive than 0 mV. Channel gating was not found to be voltage-dependent or Ca++-dependent; in inside-out patches channel gating persisted when cytosolic Ca++ concentration was buffered to less than 10'9M. The ionic permeability of the channel was investigated using inside-out patches. The channel discriminated poorly among several monovalent cations, as \ well as Ca++. The channel was not measurably permeant to the anions Cl" or gluconate. Under biionic conditions with Na+ in pipette and either Na+, K+, Li+ or Cs+ in the bath, the channel permeability to K+, Li+ and Cs+ was I. 85, 1.91 and 1.47 relative to Na+, respectively. The channel permeability to Ca++ (relative to Na+) was 1.88 measured with Ca++ on the inside and Na+ on the outside face of inside-out patches. In the inside-out patch inward rectification of the single-channel current-voltage relationship was dependent on Mg++; omission of Mg++ from the saline on the cytosolic face of the patch membrane removed inward rectification. In cell-attached patches, channel open probability was increased by bath stimulation with 1 nM angiotensin II. These results demonstrated that rat adrenal glomerulosa cells express a Ca++ permeant, nonselective cation channel that may be involved in mediating angiotensin II-induced aldosterone secretion.
Li, Fang, "Nonselective cation channel in zona glomerulosa cells of rat adrenal glands : its characteristics and possible function in aldosterone secretion" (1996). Graduate Research Theses & Dissertations. 4132.
vii, 69 pages
Northern Illinois University
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