Studies on responsiveness of hepatoma cells to catecholamines. II. Comparison of .BETA.-adrenergic responsiveness of rat ascites hepatoma cells with cultured normal rat liver cells.

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Abstract
The pharmacological properties of .beta.-adrenoceptors in rat ascites hepatoma cells were compared with those in normal liver cells which were cultured for 24h after collagenase digestion. Adenylate cyclase in the homogenates of cultured normal rat liver cells and rat ascites hepatoma cells, AH44, AH66, AH109A, AH130 and AH7974, were all activated by isoproterenol or NaF to different degrees. The enzyme in rat liver cells was activated by several .beta.2-agonists but those in all heptoma cells hardly responded. Furthermore, salbutamol, a .beta.2-partial agonist, antagonized the cyclase activation by isoproterenol in AH130 cells. The Kact value of isoproterenol for the activation of adenylate cyclase in AH130 cells was smaller than that of rat liver cells. A comparison of the K1 values of .beta.-antagonists for the inhibition of isoproterenol-stimulated cyclase activity shows that while the K1 values of propranolol and butoxamine in AH130 cells were simlar to those in rat liver cells, a significant difference was observed in the values for .beta.1-selective antagonists between AH130 cells and rat liver cells. The K1 values of metoprolol and atenolol for AH130 cells were 137- and 90-fold lower, respectively, than for normal rat liver cells. These findings strongly suggest that .beta.-adrenoceptors in rat ascites hepatoma cells including AH130 cells have similar properties to the mammalian .beta.1-receptor.