Alpha-1 adrenergic receptors in the nonfailing and failing human heart.
We examined alpha-1 adrenergic receptor density in ventricular myocardium from nonfailing and failing human hearts, utilizing the alpha-1 radioligand [125I]IBE2254. The alpha-1 receptor population comprised a relatively small portion of the total adrenergic receptors, 14.6 +/- 1.9%. However, in failing human ventricular myocardium the alpha-1 adrenergic receptor population constituted a much greater portion, 27.3 +/- 2.1% (P less than .01). The reason for the increased proportion of alpha-1 adrenergic receptors was not that the total concentration of alpha-1 receptors was increased, but instead was due to selective down-regulation of the beta-1 adrenergic receptor population. Beta-2 adrenergic receptors behaved similarly to alpha-1 adrenergic receptors in the failing human heart, and were increased in proportion and unchanged in total number. Additionally, the ability of alpha-1 stimulation to increase the incorporation of label from [3H]inositol into inositol phosphates was examined in tissue homogenates. Maximal doses of norepinephrine produced only marginal stimulation of phosphatidylinositol hydrolysis, in contrast to a more substantial response produced by muscarinic stimulation. We conclude that human ventricular myocardium contains alpha-1 adrenergic receptors that 1) are of relatively low density, 2) are unchanged in density by heart failure and 3) mediate relatively low-level stimulation of phosphatidylinositol hydrolysis.
Bristow
M R
MR
Cardiology Division, University of Utah School of Medicine, Salt Lake City.
Minobe
W
W
Rasmussen
R
R
Hershberger
R E
RE
Hoffman
B B
BB
D002217:Carbachol / Q000494:pharmacology; D006333:Heart Failure / Q000378:metabolism*; D006801:Humans; D020120:Iodocyanopindolol; D009206:Myocardium / Q000032:analysis*; D009638:Norepinephrine / Q000378:metabolism / Q000494:pharmacology; D010627:Phenethylamines / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism; D010869:Pindolol / Q000031:analogs & derivatives / Q000378:metabolism; D011942:Receptors, Adrenergic, alpha / Q000032:analysis*; D011943:Receptors, Adrenergic, beta / Q000032:analysis; D044024:Tetralones
D010627:Phenethylamines; D010716:Phosphatidylinositols; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D044024:Tetralones; C010652:BE 2254; D020120:Iodocyanopindolol; D002217:Carbachol; D010869:Pindolol; D009638:Norepinephrine