Experimental conditions influence [3H]-dihydroalprenolol binding characteristics to living HeLa cells due to...

Harvesting of plated growing HeLa cells, followed by incubation of these cells without any addition at 37 degrees C was found to cause changes in the cell shape. This phenomenon is accompanied by a diminished binding of the beta-adrenergic antagonist [3H]-dihydroalprenolol and the alpha-adrenergic antagonist phentolamine to a binding compartment not representing beta-adrenergic receptors. These binding sites have a high affinity for hydrophobic agents and most probably represent lipophilic structures in the cellular membrane. Changes in the cell shape obviously cause alterations in the physical properties of the plasma membrane. This might lead to misinterpretations of the results from experiments in which the redistribution of beta-adrenergic receptors is followed during incubation with agonists, as receptor occupation with subsequent receptor redistribution is possibly accompanied by effects on the membrane microviscosity. It is concluded that investigations performed in order to follow physiological events like receptor redistribution and desensitization processes, may be obfuscated by changes in the normal physical state of the living cells.