Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
Board

Metalloporphyrins, especially zinc protoporphyrin XI (Zn-PP-IX), have been widely used as the specific blocker of heme oxygenase (HO) to reduce the endogenous generation of carbon monoxide (CO). In the present study, it was found that Zn-PP-IX induced a concentration-dependent (10 µM to 300 µM) transient increase in intracellular free calcium concentrations, [Ca2+]i, in cultured vascular smooth muscle cells (SMCs) from rat tail artery. This effect was not extracellular calcium dependent and was blocked by thapsigargin. The Zn-PP-IX-induced intracellular calcium release was unlikely mediated by HO activities since that (1) bathing the vascular SMCs with the CO-containing Earle's solution did not induce any changes in [Ca2+]i; that (2) Zn-DPBG, but not Sn-PP-IX, induced a similar transient increase in [Ca2+]i in these vascular SMCs; and that (3) light-treated Zn-PP-IX still induced a transient increase in [Ca2+]i in vascular SMCs. It is important that when evaluating the biological functions of endogenous CO, a conclusion should not be readily made solely based on the effect of Zn-PP-IX even at relatively low concentrations. (Supported by Heart & Stroke Foundation of Canada).

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Presentation Number SAwu0210
Keywords: Calcium, SMCs, CO, Zn-PP-IX