Receptors
Receptor:Receptors
are macromolecular structures which are protein or lipoprotein in
nature,situated on the cell membrane or with in the cell (cytoplasm,nucleus)
with which the drug binds mostly reversibly or irreversively & from a drug
receptor complex,that initiates a chian of leading to the characteristic events
of drug.
Location
of receptor:
·
On cell
membrane:Insulin re,Na-K ATPase.
·
Within
cytoplasm:Steroid receptor.
·
Within nucleus:Thyroid
receptor.
Classification
of receptor:Broadly
[A]Primary/Specific
receptor:
1)
Physiological/pharmacological/active
receptor:Drugs selectively combine with these receptors & produce
action.They are only 1-2%eg.adrenergic re,histamin re.
2)
Spare/Reserve
receptor:Anatomically & functionally these re.are same as phy/ pharmacological
re.But they do not act normally.They come into play only when pharmacological
re.are exhausted or blocked.About 80-90%.eg.nicotinic re.80-90% insulin re.
[B]Secondary/non
specific/silent/dead receptor:
1)
Any drugs can combine
with these re.So these re are non-specific.
2)
The drug-receptor
complex is pharmacologically inert/inactive
& does not produce any action.So the re are called silent or dead.
3)
The re act inly as
store house of drugs & prolongs the pharmacological effect.eg. plasma
proteins.
Functional
classificational:
1)
Regulatory protein:
·
Autacoids.
·
Hormone.
2)
Enzyme:
·
Dihydrofolate
reductase(re for drug-methotexate)
·
Acetyl-transferase(re
to Ach).
3)
Transport proteins:
·
channel.
·
channel.
·
-
ATPase(re for omeprazoel).
4)
Structural protein:
·
Microtubules.
·
Tubulin(re.for
cochicine)
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