Slide 1KidneyKidneySlide 4Slide 5NephronSlide 7Slide 8Slide 9Response to InjuryAcute Renal FailureSlide 12Slide 13Slide 14Biochemical Mechanism of Renal Cell InjurySlide 16Adaptation to toxic insultSlide 18Slide 19Chronic Renal FailureAssessment of NephrotoxicityAssessmentSlide 23AssessmentSlide 25Specific NephrotoxinsSpecific NephrotoxinsSpecific NephrotoxinsSpecific NephrotoxinsEthylene glycolMethodsMethods (cont.)Methods (Cont)Toxicology of the KidneyDavid Shubert Ph.D.125 Sherman Annex [email protected]•Excretion of wastes•Regulation of extracellular fluid volume•Electrolyte composition•Acid-base balance - ph•Renin – blood pressure•Erythropoietin hormone that regulates red blood cell production•Activating Vitamin D to 1,25-dihydroxy vitamin D3Kidney•Functional Anatomy•Cortex –90% of blood flow – will receive higher amount of toxicant •Medulla – 6-10% blood flow – high luminal conc. Of toxins and time•Papilla – 1-2% blood flow - same•Nephron •Vascular element- renal artery branchesaffrent and efferent arteries• Glomerulus- workhorse large molecules not filtered (albumin) small freely filtered (lnulin)•Tubular element- starts with proximal tubuleNephron•Glomerulus – basic filtering unit•Proximal tubule – duct system•Loop of Henle- hairpin bend in renal medulla (drugs effect this area)•Distal Tubule and Collecting duct – fine regulation of volume and compositionResponse to Injury•Acute Renal Failure most common manifestation abrupt decline in GFR•Adaptation unilateral nephrectomy GFR in remaining kidney increases by 40-60% to compensate•Chronic Renal Failure progressive deterioration of renal function (analgesics, lithium)Acute Renal Failure•Abrupt decline in glomerular filtration rate with resulting azotemia abnormal levels of urea, creatinine and other nitrogen rich compounds •Hypoperfusion/hypofiltration- decrease in prefusion of the kidney – hemorrhage, shock, volume depletion•Acute tubular necrosis- death of tubular cells, chemicals and filtered proteins are nephrotoxic•Obstruction tubular cast increases tubular pressure filtration can eventually cease•Tubulointerstital nephritis affecting the interstitium of the kidneys surrounding the tubules- infection - medicationBiochemical Mechanism of Renal Cell Injury•Toxic injury•Loss of polarity, tight junction integrity•Cell death•Necrosis – cell swelling, rupture, inflammation•Apoptosis – programmed cell death, cell shrinkage, chromatin condensation, DNA fragmentation•Sloughing of viable cells•Cast formation and tubular obstructionAdaptation to toxic insult•Unilateral nephrectomy•GFR increases in remaining kidney 40-60%•Apoptosis•Oncosis•Adaptation•Cellular adaptation•Metallothionein Induction cysteine rich protein, golgi apparatus (membrane bound)•Cadmium•Stress protein Induction•Heat-shock proteins – proteins induced by stress, involved in folding and unfolding if other proteins (Hsp60, Hsp70, Hsp 80 kD)•Glucose-regulated proteinsChronic Renal Failure•Progressive deterioration of renal function•Long term analgesic•Acute renal failure has after large dose•Analagesic nephropathy – long term consumption •Interstitial nephritis – edema with infiltration of inflammatory cells•Lithium•Cyclosporine treatmentAssessment of Nephrotoxicity•Serum chemistry – look at creatinine in blood and urea levels in plasma. •Urinalyses – non- invasive assessment of overall renal functional integrity •Urine volume•Osmolality •pH•Electrolytes•Glucose •ProteinAssessment•Glucosuria (glucose in urine- if not reabsorbed then )•Chemically induced defects in proximal tubular reabsorption of sugar•Proteinuria•High molecular weight •Ex: Albumin• Glomerular damage (big things are going through)•Low molecular weight•Ex: Beta 2-microglobulin•Proximal tubular injury (because they got reabsorbed here.)Assessment•Glomerular filtration rate•Direct (in urine)•Inulin clearance – freely cleared – naturally occurring polysaccharide – not metabolized •Creatinine clearance•Indirect (in blood)•Blood urea nitrogen (BUN)•Serum Creatinine concentrations• Cystatin C (new biomarker)•Biomarker of kidney functionSpecific Nephrotoxins•Heavy Metals role of metallothioneins have a high affinity for cadmium and other heavy metals and they are inducable•Cadmium metallothioneins protection – nonsmoking humans – primarily food, half life 10 years, increase in urinary glucose, amino acids and calcium excretion •Chromium•Lead•Mercury – uptake very rigid, bound to glutathione, cysteine, or albumin – proximal tubular necrosis and Acute Renal Faliure 24 – 48 hrs•UraniumSpecific Nephrotoxins•Alpha 2u gobulin nephropathy, major urinary protein, nephropathy •-synthesized in liver (male rats) androgen control, freely filtered. •Normally reabsorbed and broken down in lysosomes, compounds bing to alpha zu and prevent breakdown by lysosomnes- leads to accumulation, single cell necrosis and formation of granular casts•Unleaded gasoline• Chronic exposure to gasoline- renal adenomas/carcinomas by nongenotoxic mechanisms •Lindane •1,4-dichlorobenzeneSpecific Nephrotoxins•Halogenated hydrocarbons•Target proximal tubule, no damage to glomerulus•Chloroform reactive intermediate binds to macromolecules•Proteinuria•Glucosuria•Increase blood urea nitrogen levels•Sex difference, linked to CYP 2E1 present in male mice, inducible in females with testosterone •Tetrafluroethylene•Metabolized and conjugated to cysteine•Target- mitochondriaSpecific Nephrotoxins•Therapeutic agents•Acetaminophen•Proximal tubule necrosis•Metabolism to reactive intermedate•Aminoglycosides antibiotics •Proximal tubule necrosis•Lysosomal alteration one hypothesis is lysosomes rupture and kill the cellEthylene glycol•Metabolized to glycolic acid and oxalic acid•Antidote : fomepizole or ethanol block the enzyme responsible for metabolizing alcohol dehydrogenase•Renal toxicity 24-72 hrs•Cytotoxic effect of glycolic acid•Oxalic acid binds to calcium forming calcium oxalate crystals- renal failureMethods•Whole animal•Anesthetized or conscious animals•Rat•Dogs•Anesthetized•Short acting anesthetic•Pentobarbital•Gaseous agents•Minute to minute controlMethods (cont.)•Clearance•Tubular Function•Renal Enzymes•Micropuncture