Sex differences in cardiac and renal responses to a high salt diet in Sprague-Dawley rats

Abstract

High dietary salt intake is an important risk factor for cardiovascular and renal diseases. However, sexual disparity exists in the response of target organs to high salt diet (HSD). To determine how sex affects cardiac and renal functions' response to HSD, 20 weanling Sprague-Dawley rats (10 males and 10 females) were divided into 4 groups of 5 rats each. The rats were fed a normal diet (0.3% NaCl) or HSD (8% NaCl) for 12 weeks. Fluid balance (FB) was determined from 24 hrs water intake and voided urine. Blood pressure (BP) was measured via arterial cannulation under anesthesia (25% w/v urethane and 1% w/v α-chloralose; 5 ml/kg, i.p). Serum levels of troponin I, aminotransaminases, creatinine, urea, uric acid and electrolytes as well as urinary concentration of albumin, creatinine, and electrolytes were measured using appropriate assay kits. Values are presented as mean ± S.E.M, compared by two-way ANOVA and Bonferroni post Hoc test. In the male rat, HSD significantly increased BP, serum: Troponin I, LDH and sodium (p < 0.05), urinary: albumin, sodium, potassium and FB (p < 0.05). In the female rat, HSD increased BP, serum: troponin I, LDH, sodium and creatinine clearance (p < 0.05), urinary: albumin, sodium and potassium (p < 0.01). However, HSD increased more, the BP, serum: Troponin I, LDH, urinary albumin and FB in male rats, while HSD increased urinary sodium more in female rats. Basal values in male vs. female of serum LDH and urinary albumin were significantly different. Thus, sex plays an important role in the response of the heart and kidney to salt stress.

Keywords: Pathology; Physiology.

Fig. 1

(a). Effect of high salt diet on Mean Arterial Blood Pressure (MABP) of male and female Sprague – Dawley rats. Significant increase (**p < 0.01; ***p < 0.001) when compared with corresponding controls. (b). Role of sex on the effect of high salt diet on MABP in Sprague-Dawley rats. ^#Significant increase (p < 0.05) when compared with female high salt diet. N = 5.

Fig. 2

(a). Effect of high salt diet on Rate Pressure Product (RPP) of male and female Sprague – Dawley rats. Significant increase (***p < 0.001) when compared with corresponding controls, (b). Role of sex on the effect of high salt diet on RPP in Sprague-Dawley rats. ^#Significant decrease when compared with male normal salt diet. N = 5.

Fig. 3

(a). Effect of high salt diet on serum Troponin I concentration in male and female Sprague – Dawley rats. Significant increase (***p < 0.001) when compared with corresponding controls, (b). Role of sex on the effect of high salt diet on serum Troponin I concentration in Sprague-Dawley. Significant increase #(p < 0.05) when compared with female high salt diet. N = 5.

Fig. 4

(a). Effect of a high salt diet on serum LDH concentration in male and female Sprague-Dawley rats. Significant increase (***p < 0.001) when compared with corresponding controls. (b). Role of sex on the effect of high salt diet on serum LDH concentration. No significant difference between male and female (p > 0.05) N = 5.

Fig. 5

(a). Effect of a high salt diet on AST concentration in male and female Sprague-Dawley rats. Significant increase (***p < 0.001) when compared with corresponding controls. (b). Role of sex on the effect of high salt diet on serum AST concentration in Sprague-Dawley rats. ^#Significant increase (p < 0.05) when compared with male on normal salt diet (control). N = 5.

Fig. 6

(a). Effect of a high salt diet on serum concentration of ALT in male and female Sprague-Dawley rats. Significant increase (**p < 0.01) when compared with female on normal salt diet (control). (b). Role of sex on the effect of high salt diet on serum ALT concentration. Significantly higher (#p < 0.05) when compared with corresponding female controls. N = 5.

Fig. 7

(a). Effect of a high salt diet on creatinine clearance in male and female Sprague-Dawley rats. Significant increase (*p < 0.05) when compared with female control. (b). Role of sex on the effect of high salt diet on creatinine clearance in Sprague-Dawley rats. ^#Significant increase (##p < 0.01; ###p < 0.001) when compared with corresponding male control on the same diets (normal or high salt diet). N = 5.

Fig. 8

(a). Effect of high salt diet on Serum concentration of Urea in male and female Sprague Dawley rats. Significant increase (***p < 0.001) when compared with corresponding controls. (b). Role of sex on the effect of high salt diet on serum urea concentration in Sprague-Dawley rats. No significant difference (p > 0.05) between male and female N = 5.

Fig. 9

(a). Effect of high salt diet on Serum concentrations of uric acid in male and female Sprague Dawley rats. Significant increase (*p < 0.05; ***p < 0.001) when compared with corresponding controls. (b). Role of sex on the effect of high salt diet on serum uric acid concentration in Sprague-Dawley rats. Significant increase (##p < 0.01) when compared with control male. N = 5.

Fig. 10

(a). Effect of high salt diet on urinary concentration of albumin in male and female Sprague-Dawley rats. Significant increase (*p < 0.05; ***p < 0.001) when compared with corresponding controls. (b). Role of sex on the effect of high salt diet on urinary albumin concentration in Sprague-Dawley rats. Significant increase (#p < 0.05) when compared with control male. N = 5.