Peripheral adrenoceptors in hypotension of hemodialyzed uremic patients.
Hypotension is a common problem in patients on hemodialysis. To further investigate this problem, the number of platelet alpha 2-adrenoceptors and the activity of lymphomonocyte beta 2-adrenoceptors were measured in 10 hemodialyzed patients with normal blood pressure and in 10 sex- and age-matched persistently hypotensive hemodialyzed patients. Density of alpha 2-adrenoceptors was assessed by the specific binding of 3H-yohimbine to intact platelets, while the function of beta 2-adrenoceptors was estimated by the production of cAMP after the exposure of lymphomonocytes to isoprenaline. The maximal number of alpha 2-adrenoceptors was increased in the hypotensive compared to the normotensive group (262.13 vs. 77.21 fmol/mg protein; p < 0.01). Plasma norepinephrine was higher in the hypotensive than in the normotensive uremic patients (640 +/- 195 vs. 344 +/- 156 pg/ml; p < 0.01). Plasma epinephrine did not differ in the two groups (90 +/- 30 vs. 94 +/- 24 pg/ml). The amount of cAMP, produced by stimulation of lymphomonocytes, was lower in the hypotensive than that in the normotensive uremic patients (7.7 +/- 2.4 vs. 15.6 +/- 5.4 pmol/10(6) cells; p < 0.002). The increased number of alpha 2-adrenoceptors together with a high level of norepinephrine and reduced activity of adenylate cyclase (coupled with beta 2-adrenoceptors) support the hypothesis that hypotension in the hemodialyzed uremic patients may be related to a defect in adrenoceptor coupling mechanisms.
Carretta
R
R
Institute of Medical Pathology, Cattinara Hospital, University of Trieste, Italy.
Fabris
B
B
Fischetti
F
F
Bardelli
M
M
Muiesan
S
S
Vran
F
F
Vasile
A
A
Campanacci
L
L
D000328:Adult; D000368:Aged; D001773:Blood Cells / Q000378:metabolism; D002395:Catecholamines / Q000378:metabolism; D000242:Cyclic AMP / Q000097:blood; D005260:Female; D006801:Humans; D007022:Hypotension / Q000503:physiopathology*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D011941:Receptors, Adrenergic / Q000378:metabolism*; D006435:Renal Dialysis; D014511:Uremia / Q000503:physiopathology*
D002395:Catecholamines; D011941:Receptors, Adrenergic; D000242:Cyclic AMP; D007545:Isoproterenol