Aging in Normotensive and Spontaneously Hypertensive Rats: Focus on Erythrocyte Properties

SIMPLE SUMMARY: We focused on changes in erythrocyte parameters—deformability, mean cell volume, and nitric oxide (NO) production by erythrocytes—in spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats, and on possible differences in these parameters as a function of age. We wanted to contribute to a more comprehensive understanding of the widely used animal model of essential hypertension—SHRs. We found that erythrocyte deformability was inversely proportional to the values of systolic blood pressure in normotensive animals, not in hypertensive ones. Regarding the relationship between the size of erythrocytes and blood pressure value, a significant negative correlation was found in SHRs, but not in WKY rats. In both normotensive and hypertensive animals, we observed a direct relationship between erythrocyte deformability and NO production by erythrocytes. Our study also suggests that age-related changes in erythrocyte deformability in both WKY and SHR are at least partially associated with changes in NO production. However, changes in NO production by erythrocytes in hypertension are probably not the primary factor affecting erythrocyte deformability. Summarizing the findings, the interpretation of the data obtained in erythrocyte parameters observed in SHRs to human hypertension needs precaution. ABSTRACT: Erythrocyte deformability, crucial for oxygen delivery to tissues, plays an important role in the etiology of various diseases. As the factor maintaining the erythrocyte deformability, nitric oxide (NO) has been identified. Reduced NO bioavailability also plays a role in the pathogenesis of hypertension. Our aim was to determine whether aging and hypertension affect erythrocyte deformability and NO production by erythrocytes in experimental animals divided into six groups according to age (7, 20 and 52 weeks), labeled WKY-7, WKY-20 and WKY-52 for normotensive Wistar-Kyoto (WKY) rats, and SHR-7, SHR-20 and SHR-52 for spontaneously hypertensive rats (SHR). The filtration method for the determination of erythrocyte deformability and the fluorescent probe DAF-2 DA for NO production were applied. Deformability and NO production by erythrocytes increased at a younger age, while a decrease in both parameters was observed at an older age. Strain-related differences in deformability were observed at 7 and 52 weeks of age. SHR-7 had reduced deformability and SHR-52 had increased deformability compared with age-matched WKY. Changes in NO production under hypertensive conditions are an unlikely primary factor affecting erythrocyte deformability, whereas age-related changes in deformability are at least partially associated with changes in NO production. However, an interpretation of data obtained in erythrocyte parameters observed in SHRs of human hypertension requires precaution.