Toxic Responses of the Kidney

Toxic Responses of the Kidney:::::
Body homeostasis is related to functional integrity of the kidney because of the kidney s role in the excretion of metabolic wastes, synthesis and release of the hormones renin and erythropoietin, and regulation of extracellular fluid volume, electrolyte composition, and acid–base balance.
Functional Anatomy:
Kidney gross examination reveals three clearly fixed anatomic areas: the cortex, medulla, and papilla. The cortex receives about 90% of blood flow, compared with the medulla (6-10%) and the papilla (1-2%). The functional unit of the kidney, the nephron, may be divided into three portions: the vascular element, the glomerulus, and the tubular element.
Pathophysiologic Responses of the Kidney
Acute Renal Failure (ARF)
It is a common signs of nephrotoxic damage, characterized by an abrupt decline in glomerular filtration rate (GFR) with resulting azotemia or nitrogenous wastes in the blood.
After exposure to a nephrotoxicant, many mechanisms may lead to a reduction in GFR. These mechanisms include prerenal vasoconstriction resulting in prerenal azotemia and obstruction caused by precipitation of a drug or endogenous compound within the capillaries before entering the glomerulus. Intrarenal factors include direct tubular obstruction and dysfunction resulting in tubular back leak and increased tubular pressure.
Tubular obstruction also may occur, the maintenance of tubular integrity is dependent on cell-to-cell and cell-to-matrix adhesion. After a chemical or hypoxic insult, adhesion of non–lethally damaged cells to the basement membrane will cause gaps in the epithelial cell lining and resulting in back leak of filtrate and diminished GFR. These detached cells also may aggregate in the tubular lumen and/or adhere or reattach to adherent epithelial cells downstream, resulting in tubular obstruction.

Alterations in the levels of a variety of vasoactive mediators may result in decreased renal perfusion pressure and renal blood flow.