Analysis of Inhibition of Proximal Tubule Sodium Reabsorption on Arterial Pressure by Using a Mathematical Model

Blood pressure in the human body is regulated by the nervous system, the renin-angiotensinaldosteron system and the kidneys. While the nervous system regulates blood pressure by affecting arterial vascular resistance, the renin-angiotensin-aldosterone system adjusts blood pressure mainly by influencing water and sodium reabsorption from the kidneys.The kidneys mainly regulate blood pressure by adjusting blood volume.The proximal tubule is an effective part of the kidney for reabsorption of water and sodium.The blood pressure lowering effects of drugs that inhibite sodium and water reabsorption from the proximal tubule have been shown in several clinical studies. In order to analyze this effect, a mathematical model of the cardiovascular system including the kidneys, nervous system and renin-angiotensin-aldosterone hormones was used. In the model, when sodium intake was increased to twice the normal level, a decrease in proximal tubule sodium reabsorption and an increase in blood pressure, extracellular fluid volume and total body sodium were observed. However, in the model, when sodium intake is increased, it has been observed that arterial pressure increases further and more sodium accumulates in the body when proximal tubule sodium reabsorption is blocked at its normal value and its decrease is prevented. This simulation result supports the clinical evidence that drugs inhibiting sodium reabsorption from proximal tubule are effective in the treatment of hypertension.