Attenuation of Oxidative Stress Contributes to Sex Differences in Renal Function between Adult Dahl S Rats
Authors: Turbeville Hannah , Garrett Michael , Sasser Jennifer 
Published: April 2020

Hypertension is a major contributor to morbidity and mortality worldwide. In the United States, age‐matched prevalence of hypertension from 2015–2016 was 45.4%. Sex differences in hypertension are well established. Before 45 years of age, more men have hypertension than women, whereas after 65 years of age, more women have hypertension than men. However, many studies in hypertension show results only in male animals. This study uses male and female Dahl SS/jr rats to test the hypothesis that the ability to attenuate levels of oxidative stress in the kidney contributes to sex differences in renal injury and function. Male and female Dahl S rats were mated non‐consanguineously and offspring were weaned at four weeks of age. All animals in all studies were on a 0.3% NaCl diet, and measurements were made in offspring at three and six months of age. Systolic BP (n=6–10/group, tail cuff) at three and six months did not differ between sexes, although male animals did exhibit a significant increase over this period (3 months; male: 159±9 mmHg; female: 165±3 mmHg, p=0.6; 6 months; male: 180±4 mmHg; female: 173±12 mmHg, p=0.5). Urine was collected (n=7–20/group) for measurement of urinary protein (Bradford assay), nephrin, and kidney injury marker‐1 (KIM‐1). Females exhibited reduced renal injury at both three and six months of age as indicated by a significant reduction in both proteinuria (3 months, male: 102±8 mg/day; female: 55±5 mg/day, p<0.0001; 6 months, male: 238±25 mg/day; female: 44±7 mg/day, p=0.0001) and KIM‐1 (3 months, male: 24±2 ng/day; female: 18±2 ng/day, p=0.03; 6 months, male: 26±2 ng/day; female: 14±2 ng/day, p=0.001). Nephrin excretion was significantly lower in females at three months (Male: 107±13 ng/day; female: 59±6 ng/day, p=0.006), but this difference did not appear at six months of age (Male: 249±53 ng/day; female: 231±57 ng/day, p=0.8), suggesting that glomerular injury progressed in both sexes by this time. Targeted RNA sequencing was performed on RNA isolated from kidney using a custom renal injury/inflammation gene panel (n=32 genes), including Sod1, 2, and 3 genes. Females exhibited higher levels of the extracellular isoform Sod3 at three (male: 0.35±0.03 normalized CPM; female: 1.44±0.2, p=0.002) and six months (male: 0.41±0.05; female: 1.29±0.11, p=0.003). However, no significant differences were seen in expression of Sod1 or Sod2. Urinary TBARS was quantified as a measure of lipid peroxidation and was significantly lower in females at three months (Male: 65±3 μM/day; female: 44±4 μM/day, p=0.009), but a difference was not present at six months (Male: 91±16 μM/day; female: 77±12 μM/day, p=0.5). These data support the hypothesis that the ability to attenuate levels of extracellular oxidative stress in the kidney contributes to sex differences in renal injury and function.

Support or Funding Information

This research was supported by the National Institutes of Health under award numbers R01HL134711 (J.M. Sasser), F30DK118864 (H.R. Turbeville), and R01HL137673 (M.R. Garrett).