Intrinsic activity

The intrinsic activity (English: Intrinsic Activity ) is a measure of the potency to alter cell function resulting from the binding of a ligand to a receptor. This level is an important parameter in the pharmacodynamics.

Reaches a ligand (eg, a drug ) to its target, it binds to the receptor and with it forms there a ligand-receptor complex. While the affinity is a measure for the binding strength between the binding partners, provides the intrinsic activity of a measure of the strength of the effect which results from said binding, dar.

The calculation is based on the intrinsic activity of the formula IA wherein the intrinsic activity, the maximal effect of the agonist Wmax and Emax is the theoretical maximum effect. The value of the intrinsic activity is therefore always between 0 and 1 has an active ingredient an intrinsic activity of 0, so it will have no effect on the receptor and is therefore a pure antagonist, the intrinsic activity is 1, then it will be the receptor binding for maximum impact, the fabric is then accordingly a pure agonist. Active ingredients, their intrinsic activity is between 0 and 1, called partial agonists. Substances that achieve the opposite effect, called inverse agonists.

It should be noted that the classical model in which a ligand " monofunctional" acts on the receptor, is no longer up to date and need to be updated. Rather, a ligand capable of different signaling pathways to address differentiated. It may well act on the same receptor on various signal paths in parallel as an agonist and an antagonist.

Since the intrinsic activity of the tissue to tissue varies, it is replaced by the term Efficacy.

Intrinsic sympathomimetic activity

Analogous to the intrinsic activity exists the concept of intrinsic sympathomimetic activity, short ISA, which is a term for the stimulatory effect of some β - receptor blockers, such as celiprolol or pindolol, on of them occupied receptors.

Swell

• Pharmacology
• Signal transduction