Adrenomedullin in Blood Plasma in Normotensive and Spontaneous Hypertensive Rats: Effect of Increased Blood Viscosity

We measured the plasma levels of adrenomedullin in normotensive Wistar rats and spontaneously hypertensive rats (SHR) was investigated, and evaluated changes in its level under conditions of increased blood viscosity. Blood viscosity was increased by the method of isovolumic hemoconcentration (replacement of 10% of circulating blood with the same volume of packed erythrocytes of donor rats). The initial concentration of adrenomedullin in Wistar rats was 1912 ± 195 pg/ml, while in SHR it was 40% lower (p = 0.007). In Wistar rats, an increase in blood viscosity was accompanied by a decrease in the concentration of adrenomedullin by 1.8 times in comparison with the initial value, while in SHR it did not lead to significant changes in adrenomedullin level. The absence of changes in the plasma adrenomedullin concentration in SHR in response to blood viscosity elevation may indicate that the mechanotransduction mechanism is excluded from the regulation of vascular tone, which is probably one of the forms of endothelial dysfunction associated with its impaired sensitivity to shear stress changes.