Journal article

Calcium dynamics and vasomotion in rat mesenteric arteries.

Smooth muscle cell calcium dynamics and diameter were measured in intact pressurized rat mesenteric artery segments during vasoconstriction and vasomotion. Arteries showed a certain norepinephrine (NE) threshold (0.3-0.4 microM) for the onset of vasomotion, during a cumulative NE concentration-response curve. This was due to a necessary [Ca2+]i threshold (increase over basal level of 22.2 +/- 2.6%) to elicit oscillations. The calcium oscillations obtained were synchronous over the entire vessel length and phase-shifted (in advance by 1.7 +/- 0.3 seconds) with respect to the diameter oscillations. A similar result was obtained using a KCl depolarization to contract the arteries, even though the [Ca2+]i threshold was much smaller in this case (increase over basal level of 9.9 +/- 4.3%), as compared with the NE-elicited vasomotion. Blockade of the Na+/K+-ATPase with 1 microM ouabain, or of the Na+/Ca2+ exchanger (NCX) with 1 microM KB-R 7943, did not abolish the calcium oscillations, thus showing that these two pumps are only modulatory elements, while on the other hand, voltage-gated calcium channels have been found to be important in the vasomotion mechanism.


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