Altered density of glomerular binding sites for atrial natriuretic factor in bile duct-ligated rats with ascites

The renal response to atrial natriuretic factor is blunted in
cirrhosis with ascites. This might be due to alterations of renal
receptors for atrial natriuretic factor. Therefore density and
affinity of glomerular atrial natriuretic factor binding sites of
bile duct-ligated rats with ascites (n = 10) and of sham-operated
controls (n = 10) were determined. Glomerular atrial natriuretic
factor binding sites were identified to be of the B-(biologically
active) and C-(clearance) receptor type. Discrimination and
quantitative determination of B and C receptors for atrial
natriuretic factor were achieved by displacement experiments with
atrial natriuretic factor(99-126) or des(18-22)atrial natriuretic
factor(4-23), an analogue binding to C receptors only. Density of
total glomerular atrial natriuretic factor binding sites was
significantly increased in bile duct-ligated rats (3,518 ± 864 vs.
1,648 ± 358 fmol/mg protein; p < 0.05). This was due to a
significant increase of C-receptor density (3,460 ± 866 vs. 1,486 ±
363 fmol/mg protein; p < 0.05), whereas density of B receptors
was not significantly different in bile duct-ligated rats (58 ± 11
vs. 162 ± 63 fmol/mg protein). Affinity of atrial natriuretic
factor to its glomerular binding sites did not differ significantly
between both groups. These data suggest that an altered glomerular
atrial natriuretic factor receptor density could be involved in the
renal resistance to atrial natriuretic factor in cirrhosis with
ascites.