ECOTOX TOXICOKINETICS PART 1 & 2
VL3, VL4
VL3, VL4
Kartei Details
| Karten | 16 |
|---|---|
| Sprache | Français |
| Kategorie | Biologie |
| Stufe | Universität |
| Erstellt / Aktualisiert | 18.05.2023 / 21.05.2023 |
| Lizenzierung | Keine Angabe |
| Weblink |
https://card2brain.ch/box/20230518_ecotox_toxicokinetics_toxicodynamics
|
| Einbinden |
<iframe src="https://card2brain.ch/box/20230518_ecotox_toxicokinetics_toxicodynamics/embed" width="780" height="150" scrolling="no" frameborder="0"></iframe>
|
Basic remarks for toxicokinetics on the organism level (4)
1. uptake > elimination -> bioaccumulation
2. the concentration of a chemical in the tissue of an organism is time & mass/size dependent
3. the elimination rate of a chemical is time & concentration dependent
4. pseudo elimination = growth dilution (persistent chemical taken up at young age -> concentration decreases with increasing growth)
How do you determine tissue concentrations & BCF (in the lab) (2 phases)
1. Phase: the exposure to the contaminant at a constant concentration -> uptake & elimination
-> wait until concentration in tissues is at SS -> calculate BCF = ctissue/cwater = ku,w/ke (BMF = ctissue/cdiet = ku,d/ke)
BUT: reaching SS can take a long time, can be more efficient to determine BCF based on uptake & elimination rates
2. Phase: depuration, contaminant is removed -> only elimination happens
Biomagnification Factor BMF & Interpretation (3)
= a measure of the increase of a chemical in organisms across trophic levels: czooplankton/cphytoplankton
BMF <1: chemical is effectively metabolized/eliminated by the organism
BMF >1: chemical accumulates from the diet in zooplankton
Example: bioaccumulation kinetics of PCB's in Rainbow Trout
- background (2)
- what concentrations do we expect in fish at SS? (2)
- How long will it take (after exposure) to eliminate 50% of the chemical? (t1/2) (1)
- researchers have found elevated PCB levels within crabs
- PCBs = endocrine disruptors
-> BCF = Corg/Cw = ku,w/ke at SS -> Corg (SS) = Cw * ku,w/ke (if you increase Cw by 2, Corg increases by 2 but BCF stays the same, as ratio)
- we have an allometric relationship for the bioaccumulation in fish; uptake rate depends on size for chemicals with logKOW >3
- t1/2 = ln(0.5)/-ke -> elimination is also heavily size/weight-dependent
Summary; both chemical (3) and biological (6) traits determine the final concentration
chemical: solubility, molecular size, partitioning behavior, degree of chlorination/halogenation (examples)
biological: organism composition (protein, lipids); feeding routes (water, sediments), diet, physiology, growth rate, feeding behavior (feeding rate), assimilation efficiency, temperature, size of organism
Define Toxicokinetics
= what a cell/organism can do to a chemical
Explain the role of the cell in toxicokinetics (4)
1. fundamental unit for providing all toxicokinetic processes
2. cell wall + membrane as important barriers for toxins
3. cell membrane & surface proteins/channels are key for uptake & elimination of chemicals/toxins
4. cellular compartments are important: depending on their composition (protein like nucleus, lipid like membrane), depends where chemical will end up
Name the 4 most important toxicokinetic processes
1. passive transport (incl. facilitated transport)
2. active transport
3. endo,- & exocytosis
4. biotransformation
