Angiotensin II receptor in primary liver cell culture: correlation between binding and biological response

Angiotensin II (AII) binding sites were characterized in intact hepatocytes using [3H]AII. Computer analysis of the saturation curve indicated the presence of only one class of binding sites with a Kd = 9.5 +/- 0.9 nM which did not change during culture up to 25 h. On the other hand, the B/sub max/ decreased from 80 +/- 12 fmol/mg of protein on freshly isolated cells to 33 +/- 5 fmol/mg of protein at 5 h culture and to 2.8 +/- 0.7 fmol/mg of protein at 25 h culture. The calcium mobilization induced by AII was measured using the fluorescent indicator fura2. AII (10 nM) increased intracellular free calcium from 160 +/- 20 nM to 319 +/- 35 nM in fresh and 5 h-cultured cells, but was without effect at 24 h. The dose response curves showed a significant decrease in the efficacy of AII to mobilize Ca2+ in 5 h-cultured cells. These data indicate a reduction in the number and perhaps coupling efficiency of AII receptors during primary liver cell culture. Experiments are being conducted to determine whether culture also induces a change in AII inhibition of glucagon-stimulated cyclic AMP accumulation