Decreased erythrocyte activity of methemoglobin and glutathione reductases may explain age-related high blood pressure.

OBJECTIVES: Erythrocytes may play an important role in regulating blood pressure as storage sites for nitric oxide (NO). The objective of this work was to determine whether factors related to variations in erythrocyte metabolism associated with NO bioavailability, such as the activity of two enzymes--methemoglobin reductase (MHbR) and glutathione reductase (GSHR)--may help explain age-related increased blood pressure. METHODS: The sample consisted of 468 individuals of both sexes, 237 hypertensive (HT) and 231 normotensive (NT), aged between 18 and 98 years (48.81 +/- 19.46). The activity of MHbR (micromol.g Hb-1.min-1) and of GSHR (micromol.g Hb-1.min-1) was determined in erythrocytes by spectrophotometry. The statistical methods used were the Mann-Whitney test, Spearman's correlation coefficient and binary logistic regression. RESULTS: In this population, age was a risk factor for hypertension (OR=1.055, 95% CI = 1.045-1.065, p < 0.001). There was a significant difference in erythrocyte activity of these enzymes between normotensive and hypertensive subjects, with lower values in hypertensives: MHbR-NT = 16.97 (3.82-34.63), HT = 16.26 (3.26-37.10), p = 0.012; and GSHR-NT=57.60 (21.59-96.58), HT = 39.26 (23.07-90.27), p < 0.001. Enzyme activity was inversely correlated with age (MHbR: r = -0.193, p < 0.001; GSHR: r = -0.757, p < 0.001). MHbR correlated directly with GSHR only in hypertensive patients (r = 0.343, p = 0.034), which was not observed in normotensives. CONCLUSIONS: Age was a risk factor for hypertension. The erythrocyte activity of glutathione and metahemoglobin reductases, essential for redox balance and nitric oxide bioavailability in erythrocytes, may contribute only partially to the increased prevalence of age-related hypertension, and other factors should be taken into consideration, such as nutrition and antihypertensive medication.

ACP1 genotype, glutathione reductase activity, and riboflavin uptake affect cardiovascular risk in the obese.

Erythrocyte acid phosphatase (ACP locus 1), also known as low-molecular-weight protein tyrosine phosphatase, has previously been associated to glycemia, dyslipidemia, and obesity. In this study, ACP1 genotype and activity were tested in 318 women aged 19 to 83 (mean, 51.74 +/- 13.44) years. ACP1 genotype was found to directly correlate to glutathione reductase activity (P < .001) and levels of low-density lipoprotein cholesterol (P = .038). Glutathione reductase activity was in turn found to correlate to a series of cardiovascular risk factors such as systolic arterial pressure (P < .001), total cholesterol levels (P = .018), and low-density lipoprotein cholesterol levels (P = .039). A possible protective effect of ACP1 genotype AA against these cardiovascular risk factors was observed in this study. Furthermore, this work hypothesizes that nutritional riboflavin uptake becomes more crucial as body mass index increases, to counteract oxidative stress and minimize cardiovascular risk. This might be especially true in ACP1 genotypes AC, BC, and CC, which might possibly show the least endogenous protection against oxidative stress.