Abstract： The present study was designed to investigate the role of protein kinase A (PKA) and phospholipase A2 (PLA2) in the stimulating effect of adenosine on the basolateral 50 pS K+ channels in the thick ascending limb (TAL) of the rat kidney.Under the anatomic microscope,the TAL was dissected.The current of 50 pS K+ channels were recorded by patch clamp technology.The protein expression of phosphorylated PKA and phosphorylated PLA2 were examined by Western blot.The results showed that cyclohexyladenosine (CHA),an analog of adenosine,increased the 50 pS K+ channel activity (P＜0.05).In the presence of H8,an antagonist of PKA,CHA did not affect the 50 pS K+ channel activity.In the presence of AACOCF3 (an antagonist of PLA2),CHA did not further increase the 50 pS K+ channel activity.CHA increased phosphorylation level of PKA,whereas inhibited phosphorylation of PLA2 in the TAL of the rat kidney (P＜0.01).Furthermore,after blocking the PLA2 with AACOCF3,CHA still increased the expression of phosphorylated PKA.On the contrary,CHA did not obviously change the expression of phosphorylated PLA2 after H8 pretrcatment.The results suggest that the stimulation of basolateral 50 pS K+ channels by CHA is mediated by the activation of PKA followed by the inhibition of PLA2 in the TAL of the rat kidney.