Angiotensin II inhibits rat arterial KATP channels by inhibiting steady-state protein kinase A activity and activating protein kinase Ce.
We used whole-cell patch clamp to investigate steady-state activation of ATP-sensitive K+ channels (KATP) of rat arterial smooth muscle by protein kinase A (PKA) and the pathway by which angiotensin II (Ang II) inhibits these channels. Rp-cAMPS, an inhibitor of PKA, did not affect KATP currents activated by pinacidil when the intracellular solution contained 0.1 mM ATP. However, when ATP was increased to 1.0 mM, inhibition of PKA reduced KATP current, while the phosphatase inhibitor calyculin A caused a small increase in current. Ang II (100 nM) inhibited KATP current activated by the K+ channel opener pinacidil. The degree of inhibition was greater with 1.0 mM than with 0.1 mM intracellular ATP. The effect of Ang II was abolished by the AT1 receptor antagonist losartan. The inhibition of KATP currents by Ang II was abolished by a combination of PKA inhibitor peptide 5-24 (5 microM) and PKC inhibitor peptide 19-27 (100 microM), while either alone caused only partial block of the effect. In the presence of PKA inhibitor peptide, the inhibitory effect of Ang II was unaffected by the PKC inhibitor Go 6976, which is selective for Ca2+-dependent isoforms of PKC, but was abolished by a selective peptide inhibitor of the translocation of the epsilon isoform of PKC. Our results indicate that KATP channels are activated by steady-state phosphorylation by PKA at normal intracellular ATP levels, and that Ang II inhibits the channels both through activation of PKCepsilon and inhibition of PKA.
Hayabuchi
Y
Y
Ion Channel Group, Department of Cell Physiology and Pharmacology, University of Leicester, PO Box 138, Leicester LE1 9HN, UK.
Davies
N W
NW
Standen
N B
NB
D000255:Adenosine Triphosphate / Q000494:pharmacology / Q000502:physiology*; D000804:Angiotensin II / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D047228:Angiotensin II Type 1 Receptor Blockers; D057912:Angiotensin II Type 2 Receptor Blockers; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D001158:Arteries / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors* / Q000502:physiology; D004338:Drug Combinations; D004553:Electric Conductivity; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006706:Homeostasis; D007527:Isoenzymes / Q000378:metabolism* / Q000502:physiology; D008297:Male; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000502:physiology; D011493:Protein Kinase C / Q000378:metabolism* / Q000502:physiology; D051744:Protein Kinase C-epsilon; D051381:Rats; D017208:Rats, Wistar; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin / Q000502:physiology
D047228:Angiotensin II Type 1 Receptor Blockers; D057912:Angiotensin II Type 2 Receptor Blockers; D057911:Angiotensin Receptor Antagonists; D004338:Drug Combinations; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin; D000804:Angiotensin II; D000255:Adenosine Triphosphate; C497257:Prkce protein, rat; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D051744:Protein Kinase C-epsilon