Effects of Dietary Salt on Blood Pressure, Heart Rate, Extracellular Fluid Volume and Glomerular Filtration Rate in Diabetic Rats

Authors: BESİM ÖZAYKAN, AYŞE DOĞAN

Abstract: In the present study, we aimed to investigate the effects of dietary salt restriction and loading on extracellular fluid volume (ECFV), blood pressure (BP), heart rate (HR), glomerular filtration rate (GFR) and renal hypertrophy in diabetic rats. Diabetes was induced by injection of streptozotocin (STZ, 65 mg/kg, iv) into male Wistar rats. Four groups were formed: a) the diabetic rats given a standard rat diet (DC), b) the diabetic rats given a high-salt diet (DHS), c) the diabetic rats given a low-salt diet (DLS), d) the nondiabetic rats given a standard rat diet (C). Salt loading and salt restriction were started 7 days after STZ injection and continued for a one-week. Diabetes did not affect ECFV and GFR values significantly, but it led to renal hypertrophy, a reduction in blood pressure (p<0.05) and a reduction tendency in HR. Salt loading caused a decrease in diastolic blood pressure (DBP) while salt restriction caused an increase in DBP, but the differences were statistically non-significant. However, these changes in opposite directions caused a significant difference between DLS and DHS. Both salt loading and restriction increased ECFV (p<0.05). GFR increased in DLS and tended to increase in DHS. We determined a significant correlation between ECFV and HR only in C (r=0.72, p<0.05) and DHS (r=-0.95, p<0.001) . We concluded that dietary salt quantity can affect DBP and ECFV levels and the alterations in ECFV may lead to changes in GFR at diabetes. In addition, both diabetes and dietary salt may modify the feedback mechanisms that operate between ECFV and HR.

Keywords: Diabetes, blood pressure, extracellular fluid volume, glomerular filtration rate, dietary salt.

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