Changes

Tissue affinity, lipid solubility and protein binding can lead to the '''accumulation''' of a toxin; examples include tetracycline, which accumulates in developing teeth/bones, organichlorides that accumulate in adipose tissues and paraquat which accumulates in the lungs.

Tissue affinity, lipid solubility and protein binding can lead to the '''accumulation''' of a toxin; examples include tetracycline, which accumulates in developing teeth/bones, organichlorides that accumulate in adipose tissues and paraquat which accumulates in the lungs.

Blood flow explains the susceptability of certain body organs to toxicity, such as the liver, kidney, brain and heart which are highly perfused, and bone which is relativley well proteed because of poor blood perfusion. Toxins that are absorbed orally pass into the portal system into the liver - the periportal area is often where highest concentrations of toxins can be found.  

Blood flow explains the susceptibility of certain body organs to toxicity, such as the liver, kidney, brain and heart which are highly perfused, and bone which is relatively well protected because of poor blood perfusion. Toxins that are absorbed orally pass into the portal system into the liver - the periportal area is often where highest concentrations of toxins can be found.  

In some tissues there are additional barriers to compounds - the blood brain barrier protects the CNS from water soluble compounds and infectious agents. Lipid soluble substances can cross this barrier - other mechanisms for crossing natural barriers include cellular transport mechanisms (e.g.cyclosporin) or endocytosis (insulin accesses cells in this fashion).

In some tissues there are additional barriers to compounds - the blood brain barrier protects the CNS from water soluble compounds and infectious agents. Lipid soluble substances can cross this barrier - other mechanisms for crossing natural barriers include cellular transport mechanisms (e.g.cyclosporin) or endocytosis (insulin accesses cells in this fashion).

Protein binding can have a number of effects on a potential toxin. When bound to a protein a toxin is usually inactivated, but it cannot be excreted in this form so accumulation can occur. Toxcity can occur when protein levels are low (hypoprotinaemia) or when another substance competeds for the protein binding site - Warfarin is 97% protein bound once absorbed, but can be displaced by NSAIDs and Sulphonamides.

Protein binding can have a number of effects on a potential toxin. When bound to a protein a toxin is usually inactivated, but it cannot be excreted in this form so accumulation can occur. Toxicity can occur when protein levels are low (hypoprotinaemia) or when another substance competeds for the protein binding site - Warfarin is 97% protein bound once absorbed, but can be displaced by NSAIDs and Sulphonamides.

===Metabolism===

===Metabolism===