Related Experiment Video
Updated: Jul 17, 2026

Long-Term Continuous Measurement of Renal Blood Flow in Conscious Rats
Published on: February 8, 2022
Interactions between sodium intake, calcium supplement, renal excretion and blood pressure in Sprague-Dawley rats
C O Oladipo1, P E Egbe, J O Ibu
1Department of Physiology, College of Medicine, University of Lagos, Idi-Araba, Lagos, Nigeria, Lagos, Nigeria. chrisladipo@yahoo.co.uk
Introduction:
The mechanisms responsible for genesis of salt-induced hypertension and its prevention by dietary calcium supplementation are still not clear. Hence, the effect of salt (NaCl) and calcium supplement on blood pressure and renal excretion were investigated.
Methodology:
Daily food consumption, water, salt and calcium intake, as well as urine volume and pH were determined. At the end of the feeding period, animals were anaesthetised and the electrocardiographic and blood pressure measurements were done.
Results:
Salt-loaded rats (SR) consumed more salt and water but less calcium, and excreted more urine and hydrogen ion than control rats (NR). There was elevation of mean arterial pressure (MAP) in SR (132.63 +/- 2.3 mmHg) compared with NR (94.00 +/- 2.2 mmHg) but there was no significant difference in their heart rates (HR) (395 +/- 11.7 vs. 429 +/- 15.4 beats/min). However, salt-loaded-calcium-fed rats (SCaR) had similar MAP as NR (99.29 +/- 1.8 mmHg) and a lower HR (379 +/- 14.9 beats/min). A reduction in water consumption and an increase in urine output as well as urinary hydrogen ion were noted in SCaR compared with SR. Calcium alone (CaR) did not have any effect on MAP (88.01 +/- 1.3 mmHg) and HR (413 +/- 7.98 beats/min). There was no difference in the organ/body-weight ratios of the aortae among the experimental rats. However, there was renal hypertrophy in SR and SCaR. Also, the hearts of SR were bigger than CaR. The mean electrical axis of hearts showed a tendency towards left ventricular hypertrophy in SR, which was greater than SCaR.
Conclusion:
The results suggest that salt loading caused renal hypertrophy and a tendency towards left ventricular hypertrophy. There are associated salt and water retention resulting in alteration of some cardiovascular function. Dietary calcium supplementation reversed these functional defects.
Related Concept Videos
Antihypertensive Drugs: Potassium-Sparing Diuretics
Antihypertensive Drugs: Action of Diuretics
Antihypertensive Drugs: Action of Calcium Channel Blockers
Introduction to Urinary System
The kidneys are bean-shaped organs located in the retroperitoneal space, on either side of the vertebral column, between the T12 and L3 vertebrae. They are partially protected by the rib cage and surrounded by perirenal fat, which provides cushioning. They are responsible for urine formation and play critical roles in regulating blood pressure, electrolyte levels, and hormone production. The ureters...
Antihypertensive Drugs: Angiotensin-Converting Enzyme Inhibitors
Regulation of Sodium and Potassium
Sodium Regulation
Sodium ions make up approximately 90% of extracellular cations, with a normal blood plasma concentration of 136–148 mEq/L. A decrease in blood volume and pressure triggers the release of renin from granular cells in the juxtaglomerular complex (JGC), primarily in...

