AJP - Renal Physiology, Vol 243, Issue 3 235-F242, Copyright © 1982 by American Physiological Society
Autoradiographic study of aldosterone and dexamethasone binding in isolated glomeruli of rabbit kidney
N. Farman, A. Vandewalle and J. P. Bonvalet
Specific binding of tritiated aldosterone ([3H]A) and dexamethasone
([3H]Dex) has been investigated in glomeruli isolated from rabbit kidney by
microdissection, using an autoradiographic method on dry film. At low
physiological concentrations of [3H]A (0.2-2 nM), no specific binding was
detected. At high concentration (24 nM), a low specific binding was found
in cytoplasm (2.5 specific silver grains/100 micrometers2) and nuclei
(3.7), which was about 10 times lower than in distal tubule. No difference
was found between superficial and juxtamedullary glomeruli. At 2.4 nM
[3H]A, no aldosterone binding was present in glomerular arterioles. Nuclear
binding of [3H]Dex was low at 3 nM (6.4 specific silver grains/100
micrometers2) and reached 23.6 at 100 nM without significant cytoplasmic
binding. Here again, this binding was much lower than in distal structures
of the nephron. In the few arterioles obtained, a clear specific nuclear
binding was observed. We conclude that the glomerulus is probably not a
target structure for aldosterone. The existence of a specific binding of
dexamethasone, although lower than in the distal tubule, raises the problem
of its physiologic significance.
