Sodium Nitroprusside-Induced Activation of Vascular Smooth Muscle BK Channels Is Mediated by PKG Rather Than by a Direct Interaction with NO

Hristo Gagov,Vladimir Serebryakov,Rudolf Schubert,Irina Gribkova

doi:10.3390/ijms23052798

Abstract

Nitric oxide (NO) is a powerful vasodilator in different vascular beds and NO-donors are widely used in clinical practice. Early data suggested that NO and NO-donors activate vascular smooth muscle high-conductance, calcium-activated potassium channels (BK channels). There exist two hypotheses explaining the effect of NO and NO-donors on BK channels—one stating that protein kinase G (PKG) mediates the effect of NO, and the other one stating that NO acts directly on the channel. Thus, the degree of contribution of PKG to the NO-induced activation of the BK channel is still not completely clear. This study tested the hypothesis that the sodium nitroprusside (SNP)-induced activation of vascular smooth muscle BK channels is fully mediated by PKG. This hypothesis was investigated using the patch-clamp technique and freshly isolated smooth muscle cells from rat tail artery. In whole-cell experiments, SNP considerably increased the outward current compared with the addition of the bath solution. SNP did not alter the current in the presence of iberiotoxin, the specific blocker of BK channels, during co-application with hydroxocobalamin, an NO-scavenger, and in the presence of Rp-8-Br-PET-cGMPS, the specific PKG-inhibitor. In inside-out patches, the activity of BK channels was increased by SNP, SNAP, and DEA-NO. However, these effects did not differ from the effect of the application of drug-free bath solution. Furthermore, a similar increase in single BK channel activity was induced by Rp-8-Br-PET-cGMPS, Rp-8-Br-PET-cGMPS together with SNP, hydroxocobalamin, and hydroxocobalamin together with SNP or DEA-NO. Finally, the activity of excised BK channels did not change in the absence of any application but was considerably increased by PKG compared with the addition of drug-free bath solution. These results suggest that NO released from NO-donors stimulates the BK current only through activation of PKG.

Highlights

The results of the present study show that application of the Nitric oxide (NO)-donor sodium nitroprusside (SNP) to freshly isolated rat tail artery smooth muscle cells increases their outward current considerably
This finding suggests that the SNP-induced increase in the outward current observed in the present study is due to a stimulation of the BK current by SNP
The present study demonstrated that SNP was unable to affect the residual outward current after pre-treatment of the cells with iberiotoxin, i.e., under conditions where BK channels are blocked

Summary

Introduction

Blood flow to different organs is regulated by changes in artery diameter. Factors released from the endothelium are among the most potent regulators of vessel diameter.Nitric oxide (NO) is a powerful endothelium-derived vasodilator in different vascular beds.For this reason, NO-donors are widely used in clinical practice.It has been shown that the vasodilating effect of NO is mediated by several mechanisms. Blood flow to different organs is regulated by changes in artery diameter. Factors released from the endothelium are among the most potent regulators of vessel diameter. Nitric oxide (NO) is a powerful endothelium-derived vasodilator in different vascular beds. For this reason, NO-donors are widely used in clinical practice. It has been shown that the vasodilating effect of NO is mediated by several mechanisms. Data suggested that NO and NO-donors activate vascular smooth muscle

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Conclusion