Hemodynamic types of cutaneous microcirculation in rats: A selective experimental study

Abstract

Background. To date, no unified approach exists to assessing the typological characteristics of peripheral microcirculation parameters, including those obtained through laser Doppler flowmetry, which diminishes the diagnostic value of the method but opens up prospects for experimental studies using laboratory animals. Objective. To identify and analyze the typological features of the cutaneous microhemodynamics of rats using laser Doppler flowmetry. Methods. A selective experimental study was conducted on 42 sexually mature male Wistar rats of mean age (192.21 ± 11.73 days) and weight (377.57 ± 21.93 g). Indices of cutaneous blood microcirculation were assessed using laser Doppler flowmetry with the laser blood flow analyzer “LAZMA-MC-1” (wavelength 0.8 μm) using the LDF 2.20.0.507WL software program (NPP Lazma, Russia). A comprehensive set of indices was recorded in the rats, allowing for the evaluation of individual-typological characteristics of cutaneous microhemodynamics: microcirculation index (average blood perfusion in microvessels per unit volume of tissue over the study period); flux (standard deviation from the arithmetic mean value of perfusion); coefficient of variation (ratio of flux to the mean value of perfusion); amplitudes of blood flow velocity fluctuations in endothelial, neurogenic, myogenic, respiratory, and cardiac frequency ranges; values of neurogenic, myogenic, and endothelium-dependent components of microvascular tone; ratio of blood inflow to venous outflow; value of nutritive and shunt perfusion; and microcirculation efficiency index. The significance of differences between index values in animals with different typological characteristics of cutaneous microhemodynamics (3 groups) was evaluated using the Kruskal-Wallis test, with the level of significance of differences between groups assessed by Dunn’s test. Results. Based on the assessment of baseline blood flow indicators in rats, three types of microcirculation were identified: aperiodic (41% of the sample), monotonic with low perfusion (33% of the sample), and monotonic with high perfusion (26% of the sample). These types, as demonstrated by wavelet analysis of the amplitude-frequency spectrum of dopplerograms, differ in their functional states concerning the main regulatory factors associated with endothelial, neurogenic, myogenic, and metabolic mechanisms and correspond to normo-, hypo-, and hyperemic hemodynamic types of microcirculation. Conclusion. The conducted study has revealed the typological features of cutaneous microhemodynamics and is instrumental in understanding the mechanisms of its functioning as well as in more effective applying laser Doppler flowmetry.

Keywords

• cutaneous microhemodynamics
• types of cutaneous microcirculation
• laser doppler flowmetry
• amplitude-frequency spectrum