AJP - Cell Physiology, Vol 258, Issue 4 C692-C699, Copyright © 1990 by American Physiological Society
Atrial natriuretic factor receptors in cultured renomedullary interstitial cells
B. M. Fontoura, D. R. Nussenzveig, K. M. Pelton and T. Maack
Department of Physiology, Cornell University Medical College, New York, New York 10021.
To gain further insight on the cell types that may mediate the effects of
atrial natriuretic factor (ANF) in the renal medulla, we determined the
distribution and function of biological (B) and clearance (C) receptors of
ANF in renomedullary interstitial cells (RMIC). Studies were performed in
the 3rd-17th passages of RMIC obtained from a primary culture of the rat
renal medulla. Electron microscopy of the cultured cells showed the typical
morphological features of RMIC "in vivo," including prominent lipid
droplets. RMIC have a very high density of high-affinity specific binding
sites of ANF-(1-28) [23,000 sites/cell; dissociation constant (Kd) = 50
pM]. There was only minimal binding of C-ANF-(4-23) (less than 2,500
sites/cell), a specific ligand of C-ANF receptors. ANF-(1-28) markedly
increased guanosine 3',5'-cyclic monophosphate (cGMP) from 1.3 +/- 0.3 to
106 +/- 22 pmol cGMP/10(6) cells [50% effective dosage (ED50) = 1.2 nM].
The effect of ANF-(1-28) on cGMP was nearly additive to that of sodium
nitroprusside and was not potentiated or antagonized by C-ANF-(4-23). The
density of guanylate cyclase-coupled B-ANF receptors and the ANF-induced
increase in cGMP in RMIC are higher than those reported to date in other
target cells. This suggests that RMIC may mediate some of the known effects
of ANF in the renal medulla.
