- hormones act thru receptors
- [ ] of free hormone and free receptor combine, need one for the other (the equation)
- will bind and dissociate so there is a rate constant (association rate constant and rate of dissociation constant)
- association constant * the product of free hormone and free receptor = dissociation constant * HR complex
K2/K1 = KD
- disocciation and association rates don’t have to be the same but they are very important
- smaller KD, smaller [ ] of hormone req’d to bind 50% of the receptors = more potent!! (the hormone itself, more effective)
- HR [ ] = hormone bound to receptor v. adding hormone graph
- the more you add, the more is bound to the receptor
- eventually receptor won’t bind anymore and you get receptor saturation (= provides no info at all)
KD: the concentration of hormones in which 50% of the receptor is bound (50% is arbituary %age, could be something else)
2 diff [ ]s of receptors, KD is the same so point at which 50% is saturated is the same but effect is very different
the 2 receptor populations are seeing the same [hormone] but the tissues respond differently
# of receptors dictates magnitude of response and sensitivity of response
- response is measured by cGMP generation, more in 100 than in 0.2
- more receptors = greater response
- the same response will occur at lower concentrations of hormones depending on # of receptors available
- more receptors available, the same response will be achieved at a lower of [H]
- affinity for the hormone of the recptor is not the most important factor attributing to the efficacy of the hormone, this is v. important for drugs
ex: why is propafol a classic agent used as an anesthetic and yet there is a 50-fold difference sensitivity b/w field
some are more sensitive that others (metabolism isn’t the only factor, basically)
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