Adipose tissue adrenoceptors

So far three subtypes of ft receptors have been identified and cloned. They differ in their distribution, the Pi type being found in the heart, the P2 in lung, smooth muscle, skeletal muscle and liver, while the P type occurs in adipose tissue. There is evidence that P2 adrenoceptors occur on the lymphocyte membrane also but the precise function there is unknown. 

The tti-adrenoceptors are located at postjunctional (postsynaptic) sites on tissues iimervated by adrenergic neurons. a2-Adrenoceptors having a presynaptic (i.e., neuronal) location are involved in the feedback inhibition of norepinephrine release from nerve terminals (discussed later). a2-Receptors also can occur postjunc-tionally. The (3i-adrenoceptors are found chiefly in the heart and adipose tissue, while (32-adrenoceptors are located in a number of sites, including bronchial smooth muscle and skeletal muscle blood vessels, and are associated with smooth muscle relaxation. 

The existence of a Ps-adrenoceptor has recently been demonstrated in human adipose tissue along with the Pi-adrenoceptor. This observation raises the possibility that eventually therapeutic drugs may selectively alter Upid metabolism and therefore provide therapeutic management of obesity. The Ps-receptor and the recently identified subtypes within the aj- and az-receptor groups ( iA, ttiB, etc.) also have not been included in the... 

The release of free fatty acids from adipose tissue (lipolysis) is mediated through (33-adrenoceptors. Isoproterenol is the most potent agonist, followed by epinephrine and norepinephrine. 

Beta3 adrenoceptor agonists Increased lipolysis and thermogenesis in adipose tissue, but disappointing results in clinical trials... 

JRS Arch, S Wilson. (33-Adrenoceptors and the regulation of metabolism in adipose tissues. Biochem Soc Trans 24 412-418, 1996. 

Cheng JT, Liu IM, Yen ST, Juang SW, Liu TP, Chan P. Stimulatory effect of D-ephedrine on beta3 adrenoceptors in adipose tissue of rats. Auton Neurosci 2001 88(1—2) 1—5. 

HagstrOm-Toft, E., Amer, P., Johansson, U., Eriksson, L. S., Ungerstedt, U., and Bolinder, J. (1992). Effect of insulin on human adipose tissue metabolism in situ. Interactions with beta-adrenoceptors. Diabetologia 35,664. 

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