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Metabolism & Toxicity
MetabolismEnvironmental
Genetic Variations
the rate of alcohol drinking
the presence of food in the stomach
the type of alcoholic beverage (Beer/Rum/Whisky)
genetic factors (variations in the principal alcohol-metabolizing enzymes)
Blood Alcohol Concentration (BAC)Decides the effects of Alcohol on various tissues.
BACDepends
on
Stomach 20%Small Intestine 80%
First pass metabolism
Elimination rate: 15mg/dl/hr
The alcohol elimination rate varies widely (i.e., three-fold) among individuals.
Bennion and Li 1976; Kopun and Propping 1977
Influenced by factors:chronic alcohol consumption
diet age
Smoking .
Interactions with metabolic pathways
Elimination of Alcohol & Toxic Metabolites
Alcohol Dehydogenase
(Cytosol)
AldehydeDehydrogenase (Mitochondria) Cytochrome P450
(Microsomes)
Catalase(Peroxisomes)
Samir Zakhari, Alcohol Research & Health, 2009
Acetaldehyde
Protein Adducts
DNA Adducts
Neuro-transmitter
Adducts
Salsolinol
1-N2, Propane deoxy guanosine
Acetate: Acetyl CoA – Lipid & Cholesterol
Biosynthesis Increase blood flow to liver.
Increased NADH/NAD+ ratio
• Hypoxic state in the cell – Lactic Acidosis
• Highly reduced cytosolic environment.
• Hypoglycemia – Due to inhibition of Gluconeogenesis.
ADH & ALDH involved in Retinol & Retinoic Acid Metabolism.
Fetal Alcohol Syndrome.
www.medicalbiochemistrypage.org
Liver damage,Hepatocellular Carcinoma
Fetal Alcohol Syndrome
Microsomal Ethanol Oxidizing System (MEOS)
PORTER:Drinking turns your nose red (Vasodilatation), it puts you to sleep (CNS depression), and it makes you urinate (Inhibits secretion of Vasopressin). Sir, it provokes and unprovokes. It provokes the desire, but it takes away the performance. It persuades you and discourages you.
Shakespeare, Macbeth, Act 2, Scene 2
MACDUFF:What three things does drink make a man do?
Acute Alcohol Intoxication:
80mg/dl: Slurred speech, incoordination, Unsteady gait.
80 -200mg/dl: Cognitive effects, Aggressiveness, Amnesia.
>200mg/dl: Nystagmus, Coma, Death.
Legal limits: 30mg/100mL.
Genetic Variations:ADH1B2: Jews
ADH1B3: African AmericansFaster Metabolism.- Elevated Aldehyde levels- Reduced
Alcohol intake.Indians: ADH1B1. No ADH1B3
ALDH2*2: Elevated Aldehyde Levels- Reduced Alcohol Intake.
Methanol
Country Liquor (Arrack, Hooch, Bootleg)
Paint Thinner
Anti freeze in Automobiles
Laboratory chemical
Food contaminants
Methanol
Toxic Dose: 20mg/dl.Lethal Dose : 300-1000mg/dl
Methanol
Optic Nerve Injury
Ocular Toxicity &
Death
Metabolic Acidosis
Methanol Poisoning
Poison Information Monograph, WHO, 2007
Treatment of Methanol Poisoning
Maintenance of Airway, Breathing, Circulation.
I.V., Sodium Bicarbonate for acidosis.
Ethanol i.v., - a competitive inhibitor of Alcohol Dehydrogenase.
4- Methyl Pyrazole – a competitive inhibitor of Alcohol Dehydrogenase.
Folate to metabolize and eliminate Formic acid.
Hemodialysis.
Further Reading:
• Goodman & Gilman, The Pharmacological Basis of Therapeutics, edn 12th.
• Overview: How is Alcohol metabolized by the body?- Samir Zakhari, Alcohol Research and Health.
Thank you