Muscle Plasticity and 𝜷_𝟐-Adrenergic Receptors: Adaptive Responses of 𝜷_𝟐-Adrenergic Receptor Expression to Muscle Hypertrophy and Atrophy

Table 1

Responses of β ₂-AR expression in skeletal muscle to anabolic and catabolic conditions.

Conditions	Species	β 2-AR		Other findings	References
		Protein	mRNA
β 2-AR stimulation
Fenoterol	Rat	↓ (FT)	n.d.		[4]
(1.4 mg⋅kg^−1⋅day^−1, 4 weeks)		→(ST)
Clenbuterol	Rat	n.d.	↓ (FT)	𝛽1-AR mRNA ↓ (LV)	[7]
(1.0 mg⋅kg^−1⋅day^−1, 10 days)			→ (ST)	β 2-AR mRNA ↓ (LV)
Clenbuterol	Rat	n.d.	↓ (FT)	GR mRNA ↓ (FT)	[8]
(1.0 mg⋅kg^−1⋅day^−1, 10 days)			→ (ST)	HuR mRNA ↓ (FT)
				AUF1 mRNA ↓ (FT)
				hnRNP A1 mRNA ↓ (FT)
Fenoterol	Rat	→ (FT, ST)	↓ (FT, ST)	G𝛼s content→(FT, ST)	[14]
(1.4 mg⋅kg^−1⋅day^−1, 2–7 days)				AC activity→ (FT, ST)
Clenbuterol	Rat	↓ (FT+ST)	n.d.		[15]
(2.0 mg⋅kg^−1⋅day^−1, 18 days)
Clenbuterol	Rat	↓ (FT)	n.d.	β 2-AR affinity→ (FT)	[16]
(4.0 mg⋅kg^−1 of feed, 10 days)
Clenbuterol	Rat	↓ (FT+ST)	n.d.		[17]
(0.2 mg⋅kg^−1⋅day^−1, 7 days)
Clenbuterol (50 μM)	Mouse (ex vivo)	Phosphorylated	n.d.	cAMP concentration ↑	[41]
Formoterol (100 μM)		𝛽2-AR ↑ (ST),		(FT, ST)
Salbutamol (500 μM)		→(FT)
Endurance training
Treadmill (12 weeks)	Rat	↓ (FT)	n.d.	β 2-AR afflnity →	[18]
				AC activty ↓
				G𝛼s content ↓
Treadmill (18 weeks)	Rat	→ (FT)	n.d.	AC activity ↑ (FT, ST)	[19]
		↑ (ST)		β 2-AR density→(acute)
Catabolic conditions
Dexamethasone	Rat	→ (FT, ST)	→ (FT)	GR mRNA ↓ (FT, ST)	[20]
(1.0 mg⋅kg^−1⋅day^−1, 10 days)			↓ (ST)	CREB mRNA ↓ (ST)
				AUF1 mRNA ↑(FT)
Dexamethasone	Rat	n.d.	→ (FT)	GR mRNA ↓ (FT, ST)	[21]
(1.0 mg⋅kg^−1⋅day^−1, 10 days)			↓ (ST)	β 1-AR mRNA ↑ (LV)
Dexamethasone	Rat	→ (FT)	n.d.	β 2-AR affinity→(FT)	[16]
(0.2 mg⋅kg^−1⋅day^−1, 10 days)
Casted-immobilization	Rat	→ (FT, ST)	→ (FT)	GR mRNA ↓ (ST)	[22]
(10 days)			↓ (ST)	GR protein ↓ (ST)
Aging	Rat	→ (FT, ST)	n.d.		[4]
Injury	Rat	↑ (FT)	↑ (FT)	G𝛼s content ↑ (FT), ↓ (ST)	[14]
(bupivacaine injection)		↓ (ST)	↓ (ST)	AC activity ↑ (FT, ST)

FT, fast-twitch muscle; ST, slow-twitch muscle; LV, left ventricle muscle. Up arrow, increase; down arrow, decrease; lateral arrow, no change. n.d., no data.