Evaluation of the function of arteriolar opening by variability in microcirculatory blood flow following angiotensin II administration in rats

Objective: We aimed to verify whether microcirculatory blood flow variability (MBFV) parameters calculated from beat-to-beat laser Doppler flowmetry (LDF) waveforms can be used instead of microcirculatory blood flow (MBF) as an index to discriminate different local microcirculatory regulation in terms of the opening condition of arteriolar openings (AO) at different sites. Methods: Angiotensin II (Ang-II) was administered to nine healthy male rats. LDF probes were placed on their renal cortex and plantar palm. The pulse width (PW) and coefficient of variance of the flux (phi) for all the pulses within a data sequence was calculated to evaluate the AO's opening condition. Results: Monitoring and prediction linear-regression analyses revealed significant positive phi-vs-mu (mean flux) and PW-vs-mu slopes at renal cortex for their changes relative to the baseline values. Conclusion: The present results suggest that these parameters calculated from the beat-to-beat LDF waveform could be useful for monitoring MBF by administering Ang-II. Moreover, possible time-domain causal relation between changes in mu and these parameters was revealed, which may allow the prediction of changes in MBF that occur 10-30 min thereafter. Deeper understanding of MBFV parameters could be useful in monitoring of progression of cardiovascular diseases and in predicting the efficacy of specific therapies.