Comparative study between heart and kidney microcirculations - Microvisualization approach

Comparative study between heart and kidney microcirculations was made by a microvisualization technique. To visualize (i) the subendocardial microcirc ulation and (ii) intrarenal microcirculation (especially afferent and effer ent arterioles), we developed a needle-lens probe videomicroscope (magnific ation: 200-400). To observe subendocardial arterioles, we introduced the needle-lens probe ( 4 mm) onto endocardial surface through the mitral valve from a small incisi on at the left atrial appendage in dogs. The diameter of subendomyocardial arterioles changed during a cardiac cycle by about 20%, while the change in subepicardial arteriolar diameter was almost negligible. The subendocardia l blood flow velocity waveform visualized by a light marker exhibited an ex clusively diastolic pattern with reverse flow during systole, while the sub epicardial flow direction was forward through a cardiac cycle. To visualize the intrarenal microcirculation, we inserted the cone-shaped n eedle-lens into kidney directly from the renal capsule in normal (WKY), spo ntaneous hypertensive rats (SHR), and streptozosin induced diabetic rats (S TZ). The afferent and efferent arteriolar sizes in WKY were nearly equal, i .e., 12 and 9 mum, respectively; however, the afferent arteriolar size in S HR was smaller (about 60% of WKY) and that in STZ was larger (120% of WKY). The diameters of efferent arterioles in both SHR and STZ were similar to W KY. In conclusion, the microcirculations in the heart and kidney are of differe nt dynamic behaviors: (i) with motion including diameter change and "slosh phenomenon" of flow waveform in the heart and (ii) without dynamic motion, but delicate vasomotor tone control of afferent and efferent arterioles in the kidney. (C) 2000 Elsevier Science S.A. All rights reserved.