The Relationship between Blood Viscosity and Blood Pressure in Normotensive and Spontaneously Hypertensive Rats

Elevated whole blood viscosity can significantly contributeto an increase in total peripheral resistance, disruption of systemichemodynamics, and development of microcirculatory disorders in arterial hypertension.Meanwhile, changes in blood viscosity (BV) also lead to changesin endothelial shear stress, which can affect vascular tone. Studiesof the correlation between changes in BV and blood pressure in animalsunder conditions of arterial hypertension have not been conducted.This work was aimed to bridge this gap using normotensive Wistarrats and spontaneously hypertensive rats (SHR) in norm, as wellas under conditions of decreased and increased BV. BV was decreased/increasedvia isovolumic hemodilution/hemoconcentration. Mean arterial pressure(MAP) was recorded using a Biopac MP150 system (USA). BV was measuredby a Brookfield DV–II+ Pro rotational viscometer (USA) at a shearrate of 450 s^–1. Normotensive rats demonstratedno statistically significant correlations between BV and MAP baselinevalues. After isovolumic hemodilution or hemoconcentration in normotensiverats, a statistically significant BV–MAP relationship was also notfound. In SHR, as compared to Wistar rats, a significant moderatepositive correlation was revealed between BV and MAP baseline values(R = 0.643, p < 0.05), persisting after bothhemodilution (R = 0.530, p < 0.05) and hemoconcentration(R = 0.689, p < 0.05). A correlation analysisshows that in SHR, unlike Wistar rats, changes in MAP passivelyfollow those in BV, which is probably due to a failure of the mechanismsof endothelium-dependent vasodilation in arterial hypertension.