Studies of blood flow in mesentery, cremaster muscle, and small bore glass tubes were performed to obtain a relationship between mean velocity (Vmean) and red cell velocity using the two-slit method under epifluorescence (Vepi) and transillumination (Vtrans) microscopy. The velocities Vepi and Vtrans obtained in vivo for 47 measurements in arterioles and venules (12- to 51-μm internal diameter) were linearly related by Vepi = 0.83 Vtrans + 0.074, and the ratio Vepi Vtrans decreased gradually with increasing vessel diameter (P ≤ 0.05). In vitro studies in tapered glass tubes (diameter 30-70 μm) were conducted for feed hematocrits (HF) from 10 to 40%. Under transillumination, Vtrans Vmean was nearly constant with an average of 1.56 ± 0.16 (SD) for all hematocrits and diameters. The velocity ratio, Vepi Vmean, however, decreased with HF from 1.8 to 0.8 as HF was increased from 10 to 40%. Theoretical considerations suggest that the variations of Vepi Vmean with tube hematocrit and diameter might result from attenuation of the excitation light by absorption and scattering by red cells, and also due to a finite depth of field of the microscope objective.
All Science Journal Classification (ASJC) codes
- Cardiology and Cardiovascular Medicine
- Cell Biology