QUANTITATIVE MORPHOMETRIC AND HISTOLOGICAL ANALYSIS OF RENAL STRUCTURE IN 9-MONTH-OLD WHITE RATS: A CONTROL GROUP STUDY

Resume. The kidneys are highly sensitive organs whose morphometric and histological characteristics reflect both physiological and pathological states. Establishing baseline values in intact animals is essential for comparative experimental studies. The study was conducted on 9-month-old white outbred rats (control group). Kidneys were removed, weighed, and subjected to morphometric and histological examination. Morphometric parameters included cortical thickness, glomerular density, glomerular diameter and area, Bowman’s capsule thickness, tubular dimensions, and vascular parameters. Histological assessment was performed using routine staining methods, and morphometric measurements were obtained using digital image analysis programs. The kidneys demonstrated a preserved architecture with a clearly distinguished cortical (72.4 ± 1.8%) and medullary structure. The absolute kidney mass was 1.65 ± 0.08 g, corresponding to 0.48 ± 0.02% of body mass. Glomerular density was 28.5 ± 1.2/mm², with a mean diameter of 82.3 ± 1.5 µm and area of 5320 ± 210 µm². The Bowman’s capsule thickness averaged 1.8 ± 0.2 µm, with a free and clear capsular space. Proximal tubules exhibited a mean diameter of 58.7 ± 2.1 µm and epithelial height of 18.5 ± 0.8 µm, whereas distal tubules had smaller diameters (45.2 ± 1.8 µm) and lower epithelial height (8.3 ± 0.4 µm). Interlobular arteries maintained normal architecture, with a media thickness of 8.5 ± 0.7 µm and media/lumen ratio of 0.32 ± 0.03. The interstitial component was minimal (6.8 ± 0.6% in cortex, 11.2 ± 0.9% in medulla), without signs of inflammation or fibrosis. The morphometric and histological features of the kidneys in 9-month-old control rats correspond to physiological norms. These findings provide a reliable baseline reference for future experimental studies involving renal pathology. Keywords. Kidney, morphometry, histology, white rats, control group, glomerulus, renal tubules, vascular architecture