Low-frequency oscillations of murine skin microcirculations and periodic changes of [Ca2+ ]i and [NO]i levels in murine endotheliocytes: An effect of provocative tests.

The five frequency intervals of skin blood oscillation were described: cardiac, respiratory, myogenic, neurogenic, and endothelial. The endothelial interval is derived into NO-independent and NO-dependent. The exact molecular, cell, or systemic mechanisms of endothelial oscillations generation are unclear. We proposed that oscillations of Ca2+ and NO in endotheliocytes may be possible sources of skin blood perfusion (SBP) oscillations in endothelial interval. To examine our hypothesis we compared the oscillations of cytoplasmic Ca2+ and NO ([Ca2+ ]i and [NO]i ) concentration in cultured murine microvascular endotheliocytes and SBP oscillations in mice. Local heating test and model hypoxia were used as tools to evaluate an interconnection of studied parameters. [Ca2+ ]i and [NO]i were measured simultaneously by Fura-2 AM and DAF-FM. The SBP was measured by laser Doppler flowmetry. The [Ca2+ ]i and [NO]i oscillations at 0.005-0.01 Hz were observed in endotheliocytes, that coincides the ranges of NO-independent endothelial interval. Heating decreased amplitude of [Ca2+ ]i and [NO]i oscillations in cells in NO-independent endothelial interval, while amplitudes of SBP oscillations increased in NO-independent and NO-dependent intervals. Hypoxia reduced the [NO]i oscillations amplitude. Heating test during hypoxia increased NO-independent endothelial SBP oscillations and decreased myogenic ones, did not effect on [NO]i oscillations, and shifted [Ca2+ ]i oscillations peak from 0.005-0.01 Hz to 0.01-0.018 Hz. We observed the [Ca2+ ]i and [NO]i oscillations synchronization within a cell and between cells for the first time. Heating abolished these synchronizations. Therefore low-frequency [Ca2+ ]i and [NO]i oscillations in endotheliocytes may be considered as modulators of low-frequency endothelial SBP oscillations.