"Kidney" - what is it, definition of the term
The renal organ in rats and mice is a paired, bean‑shaped excretory gland that filters blood, removes metabolic waste, controls fluid and electrolyte balance, and generates urine for elimination.
Detailed information
The renal organ in rodents consists of a pair of bean‑shaped structures located retroperitoneally. Each unit contains a cortex, medulla, and pelvis, with the cortex housing glomeruli and the medulla composed of parallel tubules and collecting ducts. Blood enters through the renal artery, branches into afferent arterioles, and reaches the glomerular capillaries where plasma filtration occurs. The filtrate passes sequentially through the proximal tubule, loop of Henle, distal tubule, and collecting duct before entering the renal pelvis and exiting via the ureter.
Key physiological functions include:
- Filtration of plasma to remove waste metabolites and excess electrolytes.
- Reabsorption of nutrients, glucose, amino acids, and the majority of sodium and water.
- Secretion of hydrogen ions, potassium, and organic acids to regulate acid–base balance.
- Production of erythropoietin, which stimulates red blood cell formation.
- Synthesis of 1,25‑dihydroxyvitamin D, influencing calcium homeostasis.
In rats and mice, the organ reaches functional maturity within the first two weeks after birth. Development proceeds through nephrogenesis, characterized by the formation of renal vesicles, comma‑shaped bodies, and S‑shaped bodies that differentiate into mature nephrons. The total nephron count differs between species: laboratory rats possess approximately 30,000–40,000 nephrons per kidney, whereas mice have about 10,000–12,000.
Experimental research frequently utilizes these animals for disease modeling. Common applications involve:
- Induction of acute renal injury through ischemia‑reperfusion or nephrotoxic agents.
- Genetic manipulation to study hereditary renal disorders, such as polycystic disease or glomerulopathies.
- Pharmacological testing of diuretics, antihypertensives, and renin‑angiotensin system inhibitors.
- Investigation of metabolic syndromes by monitoring changes in filtration rate, electrolyte handling, and hormone production.
Histological examination typically employs hematoxylin‑eosin staining for structural assessment, periodic acid‑Schiff for basement membrane integrity, and immunohistochemistry to detect specific transport proteins. Electron microscopy reveals podocyte foot process architecture and endothelial fenestrations essential for selective filtration.
Blood chemistry in these models provides quantitative markers of organ function: serum creatinine, blood urea nitrogen, electrolytes, and urinary protein excretion. Adjustments in diet, fluid intake, and environmental temperature can influence these parameters, requiring standardized conditions for reproducible results.
Overall, the renal system of rats and mice offers a compact, well‑characterized platform for exploring fundamental kidney physiology, pathophysiology, and therapeutic interventions.