AJP - Renal Physiology, Vol 251, Issue 4 594-F602, Copyright © 1986 by American Physiological Society
Distinct localization of atrial natriuretic factor and angiotensin II binding sites in the glomerulus
C. Bianchi, J. Gutkowska, G. Thibault, R. Garcia, J. Genest and M. Cantin
A comparative study of the localization of 125I-labeled atrial natriuretic
factor (ANF) and 125I-labeled angiotensin II (ANG II) binding sites in the
glomerulus of the rat, after an intravascular injection, has been done by
ultrastructural radioautography. 125I-ANF binding sites are localized
predominantly on the podocytes of the visceral epithelium (63%) followed by
the endothelium of capillaries (14%), the parietal epithelium (13%), and
finally mesangial cells (10%). In a comparative study, it was confirmed
that 125I-ANG II uptake is localized predominantly on mesangial cells (60%)
followed by epithelial visceral cells (23%) and the endothelium of
capillaries (16%). Using isolated rat glomeruli, it was confirmed that ANG
II decreases glomerular size (maximum effect of 15%) with an apparent half
maximum effective concentration (EC50) between 10(-9) and 10(-8) M.
Although ANF alone has no apparent effect on glomerular size, it inhibits
the contractile effect of ANG II with a half maximum inhibitory
concentration (IC50) between 10(-11) and 10(-10) M. These results suggest
that an intraglomerular mechanism other than glomerular arteriolar
resistance may be involved in the modulation of glomerular filtration rate
by ANF. The presence of 125I-ANF uptake mainly in foot processes of
visceral epithelial cells of glomeruli in vivo and the inhibition of ANG II
decrease in glomerular size by ANF in vitro raise the possibility that ANF
may regulate the ultrafiltration coefficient by two mechanisms: modulation
of glomerular permeability, and surface area.
