We have developed a new method of aortic pulse wave velocity measurement (PWV) as a means of evaluating experimental arteriosclerosis and established a practical noninvasive procedure for sequential determination of the progress of arteriosclerosis. Further, we have also established a procedure for quantitative, histochemical determination of the main aortic wall constituents, such as elastin (EB), collagen (CL), acid mucopolyssacharides (AMPS), glycoprotein (GP), smooth muscle (SM) and deoxyribonucleic acid (DNA). In this investigation we determined changes in aortic pulse wave velocity in groups of healthy and arteriosclerotic rabbits and quantitatively determined the six arterial wall constituents to clarify the diminished function and degeneration of sclerosed arteries in the rabbit.
Materials and Methods
The animals used in this investigation consisted of 5 healthy Japanese native white rabbits at 38 months of age and 5 arteriosclerotic ones. An artificial carotid arterial loop was produced in all the 10 rabbits so that blood pressure and pulse wave velocity measurements might be obtained. Experimental arteriosclerosis was induced through combination of three methods; hypoxia (induded by N
2 gas inhalation), tissue impairment (by intramuscular administration of epinephrine), and vasovasorum occlusion and intimal thickening (by oral administration of cholesterol). Pulse wave velocity and blood pressure measurements were obtained twice weekly, and both healthy and diseased groups were sacrificed 22 weeks after initiation on study and specimens of arterial wall constituents were obtained from isolated aortas. The relationships between kinds of stainning and absorption wavelengths were as indicated below: Weigert for EL; 590nm, van Gieson for CL; 563nm, Alcian Blue for AMPS; 608nm, PAS for GP; 565nm, Azocarmin G for SM; 545nm, and Schiff for DNA; 512 and 570nm. Quantitative determinations were carried out, using MSP and scanning each tissue specimen at 20 to 30 sites with a set of a 10-power object lens, a 10-power condenser and a pinhole turret No. 6. The levels of arterial wall constituents were expressed in absorbance.
Results
1. The systolic pressure for the healthy rabbits ranged from 110 to 140mmHg and the diastolic pressure, from 60 to 80mmHg, as is exactly the case with adult humans. Both systolic and diastolic blood pressures in the arteriosclerotic rabbits were higher by 10% than in the healthy rabbits.
2. Initial values of PWV obtained in both groups ranged from 7.5 to 8.0m/sec. However, whereas PWV values remained unchanged in the healthy group, the arteriosclerotic group had a gradual increase, and at 4 weeks the difference was statistically significant (p<0.05 to 0.01). Ultimately at 22 weeks (end of the study) the mean PWV value stood at 7.58±0.2m/sec for the healthy group, while it was 8.76±0.43m/sec (p<0.001) for the arteriosclerotic group.
3. The differences in the levels of six arterial wall constituents between the two groups were as indicated below.
4. To clarify the implications of changes in the levels of six constituents, the rate of contribution to sclerosis was determined for each of the constituents. The rate of contribution for the first principal component by multivariate statistical analysis was 62.27%. DNA, SM, CL and EL were decreased by 0.889, 0.832, 0.819 and 0.812 respectively, while GP and AMPS were increased by 0.824 and 0.496 respectively. Accordingly, the first principal component can be considered important as a sclerosis-promoting factor. The rate of contribution for the second principal component was 14.47%. This value is not high enough to implicate the second principal component as a positive sclerosis-promoting factor, but the total contribution of the first and second principal components by was as high as 77.74%.
5. Further, the linear equation of estimation and coefficient of correlation derived from the PWV values and scores
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