The erythrocyte in aging

Red cell shape changes in the blood of people 60 years of age and older imply a role for blood rheology in the aging process

Five-drop samples of venous blood, which was fixed immediately, were obtained from 76 males and 91 females who were 60 years of age and older, and did not take part in competitive sport, and from 73 males and 50 females participating in the Golden Oldies Soccer tournament or in the Dunedin Masters' Games. Most participants were nonsmokers. Those in the competitive group indicated a higher level of activity than those in the noncompetitive group, and the majority of participants indicated high levels of well-being. 30 different medical diagnoses were recorded including hypertension (36 cases), arthritis (17 cases), diabetes (6 cases), angina (6 cases) and coronary heart disease (7 cases). Most samples had high values for flat cells. Increased values for cells with altered margins were found in 7 males and 7 females, while 6 males and 1 female sample had increased values for cells with surface changes. It is concluded that some factor or factors in the aging process are responsible for red cell shape transformation. As high values for flat cells occur in people with chronic disorders, the lack of symptoms or evidence of dysfunction in people over 60 implies that survival is a consequence of having larger than usual capillaries.

The cutaneous microcirculation of the forearm in young and old subjects

Previous studies have shown a reduced cutaneous circulatory response to direct heat stress in the forearm circulations of older (60 to 80 year) subjects. The purpose of this study was to test the hypothesis that this aging effect is due to a reduced ability of the cutaneous microvessels in the forearm to respond to direct heat. Two groups of male subjects consented to participate; a group of 15 young individuals (Y; 20-39 year) and a group of 11 older (O; 60-79 year) individuals. The subjects rested in a supine position with the right forearm situated on the stage of a Leitz epiilumination microscope which was used to view the superficial cutaneous microvessels. The width of the red cell column (WRC), an index of vascular diameter, and the blood cell velocity (BCV) within the microvessels were measured by videomicroscopy at the presenting skin temperature (Ts) of 32 degrees, and then again after Ts had been elevated to 35 degrees then 40 degrees. At a Ts of 32 degrees, WRC and BCV for the Y group, respectively, averaged 6.6 microns and 0.22 mm/sec. Corresponding averages for the O subjects were 8.4 microns and 0.17 mm/sec. Between-group differences were not significant. At a skin temperature of 40 degrees, BCV was significantly higher compared to that at 32 degrees and 35 degrees for both groups (P less than 0.05); whereas, WRC did not significantly change. There were no significant between-group differences in BCV at the higher two temperatures. These results argue against a diminished blood flow response of superficial microvessels being responsible for the reduced cutaneous circulatory response to heat stress in older individuals.

The effect of donor age on the packing susceptibility of erythrocytes

The study of 411 healthy persons indicates that erythrocyte susceptibility to centrifugal packing at 200 g increases with age, evidencing an age-related decrease in red cell deformability. Positive correlations between donor age and blood plasma fibrinogen concentration and erythrocyte sedimentation rate were confirmed. The impairment of red cell deformability may affect the circulatory efficiency in the aged.

The effect of donor age on the flow properties of blood. Part I: Plasma and whole blood viscosity in adult males

The relationship between blood viscosity and age was studied using heparinized blood samples obtained from 50 normal male blood donors between the ages of 20 and 65 years. There was a slight but significant decline in packed cell volume (hematocrit) with age. Plasma viscosity showed no significant variation with donor age, but the viscosity of blood samples standardized to a packed cell volume of 45 ml/dl showed an increase as the age of the donor rose. The age-related trend to a higher viscosity was present at shear rates below 46 s-1, but not at higher shear rates. This shows that with age there is a rising trend in the red cell contribution to blood viscosity, which is not dependent on the packed red cell volume; this component increases across a wide age range in early and middle adult life, and is not a characteristic appearing exclusively in later age periods. The tendency for the viscosity trend to be greater at lower shear rates indicates increased shear thinning in blood obtained from older subjects, the cause of which may be either diminished red cell deformability in these subjects, or an increased tendency to form aggregates at low shear rates.

Increase of size and dry mass of human erythrocytes depending on age of donors

The size and dry mass of erythrocytes from the blood of men of various ages were measured by means of microscopic interferometry. The donors age-dependent increase of erythrocytes size and dry mass was found.

Increase of size and dry mass of mouse erythrocytes depending on age of donors

It was found that during aging of mice the size and the dry mass of their erythrocytes increased. Similarity of this phenomenon to that observed during aging in vitro and in vivo is suggested.

Red blood cell glucose-6-phosphate dehydrogenase activity in aged humans

The enzyme glucose-6-phosphate dehydrogenase (G6PD) was assayed in the circulating erythrocytes of 38 20-to 30-year-old subjects and 29 80- to 90-year-old subjects. The red blood cell G6PD activity of an aged-unbiased erythrocyte population in the young group was found to be significantly higher than in the older group (5.46 +/- 1.06) vs (4.31 +/- 0.99) (P less than 0.001), respectively (mean +/- SD). No significant difference was observed between the mean enzyme values of the male and female subjects in the two age groups. Since the mature red blood cell is devoid of regenerative capabilities, one may propose an explanation for this observation that implicates either an alteration in G6PD synthesis in the erythrocyte precursor cells in aged hosts, and/or the presence of an inhibitory factor that has the effect of decreasing the assayed activity for this enzyme.