guanosine-diphosphate and 1-oleoyl-2-acetylglycerol

1. The effects of the vasoconstrictor angiotensin II (Ang II) on whole-cell ATP-sensitive K+ currents (IK,ATP) of smooth muscle cells isolated enzymatically from rat mesenteric arteries were investigated using the patch clamp technique. 2. Ang II, at a physiological concentration (100 nM), reduced IK,ATP activated by 0.1 mM internal ATP and 10 microM levcromakalim by 36.4 +/- 2.3%. 3. The protein kinase C (PKC) activator 1-oleoyl-2-acetyl-sn-glycerol (OAG, 1 microM) reduced IK,ATP by 44.1 +/- 2.7%. GDP beta S (1 mM), included in the pipette solution, abolished the inhibition by Ang II, while that by OAG was unaffected. 4. Pretreatment with the PKC inhibitors staurosporine (100 nM) or calphostin C (500 nM) prevented the Ang II-induced inhibition of IK,ATP. 5. Ang II inhibition was unaffected by cell dialysis with PKA inhibitor peptide (5 microM), and the PKA inhibitor Rp-cAMPS (100 microM) did not reduce IK,ATP. 6. Our results suggest that Ang II modulates KATP channels through activation of PKC but not through inhibition of PKA.

Topics: Adenosine Triphosphate; Angiotensin II; Animals; Cromakalim; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Diglycerides; Enzyme Inhibitors; Glyburide; Guanosine Diphosphate; Hypoglycemic Agents; Male; Membrane Potentials; Mesenteric Arteries; Muscle, Smooth, Vascular; Naphthalenes; Patch-Clamp Techniques; Potassium; Potassium Channel Blockers; Potassium Channels; Protein Kinase C; Rats; Rats, Wistar; Staurosporine; Thionucleotides; Vasoconstrictor Agents; Vasodilator Agents

We explored the possibility that muscarinic receptor stimulation can inhibit ATP-sensitive K+ (KATP) channels in smooth muscle cells from guinea pig urinary bladder. Whole cell K+ currents were measured in smooth muscle cells isolated from the detrusor muscle of the guinea pig bladder. Stimulation of muscarinic receptors by carbachol (CCh; 10 microM) inhibited KATP currents by 60.7%. Guanosine 5'-O-(2-thiodiphosphate) in the pipette (internal) solution prevented the CCh-induced inhibition of KATP currents. Activators of protein kinase C (PKC), a diacylglycerol analogue, and phorbol 12-myristate 13-acetate inhibited KATP currents by 63.5 and 73.9%, respectively. Blockers of PKC (bisindolylmaleimide GF-109203X and calphostin C) greatly reduced CCh inhibition of KATP currents. We propose that muscarinic receptor stimulation inhibits KATP channels in smooth muscle cells from urinary bladder through activation of PKC.

Topics: Adenosine Triphosphate; Animals; Benzopyrans; Carbachol; Cromakalim; Diglycerides; Glyburide; Guanosine Diphosphate; Guinea Pigs; In Vitro Techniques; Indoles; Maleimides; Membrane Potentials; Muscarinic Antagonists; Muscle, Smooth; Potassium Channels; Protein Kinase C; Pyrroles; Receptors, Muscarinic; Tetradecanoylphorbol Acetate; Thionucleotides; Urinary Bladder