Common components of patch-clamp internal recording solutions can significantly affect protein kinase A activity

Common components of whole-cell internal recording solutions were tested bo th in vitro and in patch-clamp experiments for their effects on the activit y of cAMP-dependent protein kinase. Potassium fluoride (KF), 440 mM trimeth ylamine chloride and exclusion of bovine serum albumin (BSA) decreased the activity of the enzyme, while ethylene glycol-bis (beta-aminoethyl ether) N ,N,N',N'-tetraacetic acid (EGTA) and the potassium salts of aspartate, gluc onate, methylsulfate and monobasic phosphate increased its activity. Additi on of KF to the internal solution produced a hyperpolarizing shift in the V -1/2 of I-h channel activation, consistent with the KF-induced reduction of protein kinase A activity. Therefore, consideration of the composition of internal solutions is warranted when studying channel physiology by patch-c lamp techniques. (C) 1999 Elsevier Science B.V. All rights reserved.