Histological Changes in the Renal Medulla and Papilla of Adult Wistar Rats Following Chronic Intake of High-Sodium Drinking Solutions

International Journal of Anatomy and Physiology | Vol. 15, No. 9, September 2026 | pp. 473–484

DOI: 10.46882/2026/IJAP/000207

Article Type: Original Research Article

Title: Histological Changes in the Renal Medulla and Papilla of Adult Wistar Rats Following Chronic Intake of High-Sodium Drinking Solutions

Names of Authors: Fatimah H. Al-Zahrani¹, Mustafa A. Al-Hassan²

Authors’ Affiliations: ¹Department of Anatomy, College of Medicine, King Saud University, Riyadh, Saudi Arabia; ²Department of Physiology, Faculty of Medicine, Cairo University, Cairo, Egypt

Abstract:
Excessive dietary sodium intake induces vascular stress and compromises the countercurrent multiplier system within the kidney. This study evaluated the structural modifications occurring within the renal medulla and papilla of adult Wistar rats following chronic consumption of a high-sodium drinking solution. Twenty-four male rats were randomly assigned to two equal groups (n = 12): a control group receiving standard tap water and a high-sodium group receiving a 2.0% sodium chloride (NaCl) drinking solution ad libitum for 12 consecutive weeks. Renal tissue sections were processed and stained with Hematoxylin and Eosin (H&E), Periodic Acid-Schiff (PAS), and Masson’s trichrome for quantitative microstructural profiling. The high-sodium group displayed severe architectural disruption within the inner medulla and papilla, characterized by lumen dilation of the collecting ducts and flattening of the principal epithelial cell height (6.10 ± 0.45 μm vs 9.85 ± 0.65 μm in controls, p < 0.01). Masson's trichrome staining demonstrated a 3.4-fold expansion of interstitial extracellular matrix deposition in the medullary space, indicating focal interstitial fibrosis. PAS staining revealed localized basement membrane splitting along the thin limbs of Henle’s loop. These histological alterations demonstrate that chronic high-sodium loading alters the specialized cell structural integrity of the renal medulla and induces tubulointerstitial remodeling, shedding light on the morphological pathways underpinning sodium-dependent renal concentrating defects.

Keywords: Renal Medulla, High-Sodium Diet, Collecting Ducts, Histological Damage, Interstitial Fibrosis, Wistar Rats

Manuscript Timeline: Received: August 24, 2026; Revised: September 19, 2026; Accepted: September 27, 2026; Published: September 30, 2026

Citation: Al-Zahrani F.H., & Al-Hassan M.A. (2026). Histological Changes in the Renal Medulla and Papilla of Adult Wistar Rats Following Chronic Intake of High-Sodium Drinking Solutions. International Journal of Anatomy and Physiology, 15(9), 473–484. DOI: 10.46882/2026/IJAP/000207

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