BIOLOGY 2B03 Lecture 7: Lecture 7 Summary

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9 Feb 2012

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Participates in every bodily function; breathing, heartbeat, digestion, vision, smell, brain, function Gpcrs interact with a ligand (signal) outside of the cell: results in change in receptor protein conformation, transduction of signal inside the cell via interaction with g-protein. Medical applications of synthetic analogs of hormones: most drugs work in 2 different ways either as agonists (mimic the natural signal) or antagonists (interfere with the natural signal) Agonist = binds to receptor and mimics normal function. Isoproterenol mimics epinephrine s relaxing effect on bronchial smooth muscle, opening air passages used in: treatment of bronchial asthma or chronic bronchitis. Many agonists are compounds that interact with a specific form of receptor but not all related variants. B1 increase the heart rate and strength of the heart beat. Pharmaceuticals can mimic epinephrine s ability to stimulate b2 adrenergic receptor but not b1. Antagonist = binds to the receptor but does no induce hormone response.

Related Questions

receptor	Agonist	antagonist


a1	Norephinephrine	Phenylephrine
a2	Phenoxybenzamine	Prazosin
B1	Clonidine	Yohimbine
	Norephinephrine	Propranolol
	Epinephrine	Metoprolol
	Isoproterenol
	Dobutamine
B2	Epinephrine	Proranolol
	Norepinephrine	Butoxamine
	Isoproterenol
	Albuterol


Nicotinic	Ach	Curare
	Nicotine
		Hexamethonium
Muscarinic	Ach	Atropine

Assume all the chemicals in the table are available to you.

You are given a piece of smooth muscle tissue, you stimulate it with Norepinephrine and find the muscle responds with contractions. Your hypothesis is that the muscle contraction is caused by the activation of Î±1 adrenergic receptors. Now you need to design an experiment protocol to test your hypothesis.

Background knowledge: The figure below is an experiment setup, the red tissue in the organ bath is the smooth muscle tissues. In this kind of experiment smooth muscle tissue is minimally stretched vertically by two hooks or clips in the organ bath filled with physiological saline solution (PSS). Agonist is added to the PSS to challenge the muscle tissue, muscle contraction is sensed by a force transducer at the top and force is recorded by a computer. Adding antagonist before adding agonist blocks agonist action. PSS may or may not be changed, it depends on your purposes, e.g. if you want to block a type receptors, then you do not want change PSS after you add antagonist to the PSS. Your correct step is that you add antagonist to PSS, wait some time, and add agonist, you keep both antagonist and agonist in the PSS so that you can judge if the receptor blockage by antagonist abolish the agonist action.

The key to this assignment is that you eliminate possible cross-activities of agonists. Cross-activity means an agonist activate more than one types of receptors, you need block each type of the receptor in order to see what type of the receptor is activate to cause contraction. This muscle tissue can have both Î± and Î² receptor types and their subtypes, you need to demonstrate convincingly that you only stimulate Î±1 receptors.

Write an experimental protocol to demonstrate your work, for each step in the protocol you write the chemical(s) you add, why you add, what result you are expecting to see e.g. contract, relax, no response. If the step is to wash the tissue with fresh PSS, then you do not need to indicate the responses.

Here is an example of the answer.

step	chemical added	response
1.	epinephrine, activate alpha and beta receptors,	blood vessel ring contract slightly.
2.	wash with PSS
3.	alpha receptor antagonist and norepinerphine, block NE activating alpha receptor.	blood vessel ring should not contract.
4.	wash with PSS
5.	â¦	â¦
6.	â¦	â¦

Discuss your protocol to show the relation between activation of Î±1 receptors and the vascular smooth muscle contraction.Design the experiemnt and its conclusion/ results.

Endocrine disrupting chemicals (EDCs) can act by binding directly to hormone receptors as hormone âmimicsâ or as âantagonistsâ. Describe the key difference in mechanism between mimics and antagonists in terms of the effects on receptor signaling. Why is it important to know the potencies of different EDCs relative to normal estrogen or other relevant hormones for understanding the potential human health effects from exposure to EDCs?

A scientist is studying the function of a type of nuclear steroid receptor protein in mouse cells. She introduces various mutations into the gene encoding the receptor protein and transfers the genes into mice. If mutations are introduced that (a) eliminate the nuclear import signal in the receptor protein or (b) alter the receptor protein surface so that the receptor can no longer interact with Hsp70 protein, how will the molecular pathway of hormone-receptor interaction be altered?

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BIOLOGY 2B03 Lecture 7: Lecture 7 Summary

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