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Supplemental Videos

Supplemental Videos for figures 3, 5, 6, and 7e.

Files in this Data Supplement:

• Video 3 - A representative artery showing the effects of 10 mM [Mg²⁺]_O on [Ca²⁺]_CYT and myogenic tone (artery diameter) in a pressurized rat small mesenteric artery. Under control conditions, the artery generated myogenic tone, and many of the cells exhibited modest Fluo-4 fluorescence (directly related to [Ca²⁺]_CYT). When [Mg²⁺]_O was elevated to 10 mM at 50 sec, [Ca²⁺]_CYT (i.e., fluorescence) in each of the myocytes declined and the artery dilated (indicated by upward movement of the artery wall). Upon restoration of normal Krebs (with 1.2 mM Mg²⁺) at 160 sec, the [Ca²⁺]_CYT in the myocytes rose and the artery constricted.
• Video 5 - A representative artery showing the effects of 10 mM [Mg²⁺]_O on 75 mM K+-induced changes in [Ca²⁺]_CYT and vasoconstriction. Under control conditions, the artery generated myogenic tone, and many of the cells exhibited moderate Fluo-4 fluorescence. When [Mg²⁺]_O was elevated to 10 mM at 21 sec, [Ca²⁺]_CYT in each of the myocytes declined and the artery dilated. Introduction of 75 mM K+-Krebs in the continuous presence of high [Mg²⁺]_O at 106 sec induced a large increase in [Ca²⁺]_CYT associated with a marked vasoconstriction. When [Mg²⁺]_OO was restored to 1.2 mM at 219 sec, [Ca²⁺]_CYT again fell to a low level, and the artery recovered myogenic tone.
• Video 6 - A representative artery showing the effects of 0.3 µM Nifedipine (Nif) on 75 mM K⁺-induced changes in [Ca²⁺]_CYT and vasoconstriction. Under control conditions, the artery generated myogenic tone, and many of the cells exhibited modest Fluo-4 fluorescence. When 0.3 µM Nif was applied, at 9 sec, [Ca²⁺]_CYT in each of the myocytes declined and the artery dilated. Elevation of [K⁺]_O to 75 mM in the continued presence of Nif at 91 sec had little effect on [Ca²⁺]_CYT in most cells, but induced modest elevation of [Ca²⁺]_CYT in a few cells. There was no arterial wall displacement (i.e., vasconstriction) under these circumstances. Following washout of the Nif and high K⁺ at 158 sec, the myocyte fluorescence slowly increased and the artery recovered myogenic tone.
• Video 7e - A representative artery showing the effects of 10 mM [Mg²⁺]_O on 5 µM PE-induced changes in [Ca²⁺]_CYT (Fluo-4 fluorescence) and diameter. Introduction of 5 µM PE at 60 sec induced a large increase in [Ca²⁺]_CYT, which then settled down to a somewhat lower, but still elevated level. Superimposed on this were relatively large [Ca²⁺]_CYT fluctuations (oscillations) which occurred simultaneously in a number of cells. [Ca²⁺]_CYT changes were associated with a large and maintained vasoconstriction (despite a slowly declining [Ca²⁺]_CYT) and vasomotion; The constriction phase of the vasomotion occurred at the peaks of the [Ca²⁺]_CYT fluctuations. Elevation of [Mg²⁺]_O to 10 mM in the presence of PE markedly lowered [Ca²⁺]_CYT and abolished the fluctuations at 185 sec; this was accompanied by a marked vasodilation that was approaching PD. When [Mg²⁺]_O was restored to 1.2 mM at 245 sec. [Ca²⁺]_CYT promptly rose again, and began to oscillate; the artery reconstricted, and again exhibited vasomotion. Upon washout of the PE at 410 sec, [Ca²⁺]_CYT again fell to a low level, the [Ca²⁺]_CYT oscillations were abolished, and the artery dilated to PD.

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