Calcium Dynamics and Vasomotion in Rat Mesenteric Arteries

Abstract

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.

Vascular reactivity of isolated rat mesenteric arterioles in the presence and absence of ouabain

“…In this study, vasomotion was observed at NE concentration range of 0.4~tM to 1 f.!M which is in agreement with Schuster's findings. The time period of diameter oscillations observed in this study was 4.0 (±1.5) seconds which is in close agreement with a time period of 5.0(± 1.1) seconds as observed by Schuster et al ( 121 ).…”

“…This finding is consistent with other studies who have reported the diameter increases as a function of intra-luminal pressure in isolated cannulated rat mesenteric arteries (5,111). Schuster et al (121) has reported that in-vitro observation of vasomotion is highly dependent on the proper handling of the vessel. The occurrence of vasomotion is highly dependent on the integrity and functionality of ion channels and gap junctions present in SMC which can be easily disrupted during the dissection and cannulation of the vessels.…”

“…In this study, vasomotion did not abolish in the presence of 1 !tM ouabain which is in contradiction with some studies (53), but consistent with others (121 ). The abolishment of vasomotion observed by some groups could be due to a difference in the tissue studied or partially impaired ves<.,el leading to abolishment of vasomotion.…”

“…Vasomotion, which is characterized by a rapid oscillation of vessel diameter, occurs on application of vasoconstrictors like NE and KCJ and is reported as a random event ( 121 ).…”

Theoretical Investigation of Intra- and Inter-cellular Spatiotemporal Calcium Patterns in Microcirculation

“…induced by NE were measured in Chinese hamster ovary cell culture . Unlike some vessels with spontaneous vasomotion, RMAs require depolarization that opens VOCCs and maintains mean Ca 2+ levels within the oscillatory window (Schuster et al 2004). In the model, NE opens NSC channels, reduces significantly membrane resistance and depolarizes SMCs in agreement with experiments (Sell, Boldt, and Markwardt 2002).…”