Identification of alpha 1-adrenoceptor subtypes in rat renal proximal tubules.
Although the existence of alpha 1-adrenoceptor subtypes has been suggested in the kidney, their characterization in the proximal tubules has not been reported. This study was undertaken to characterize the alpha 1-adrenoceptor subtypes in the renal proximal tubules. [3H]Prazosin bound to proximal tubules with a KD of 106 +/- 17 pM and a Bmax of 152 +/- 9 fmol/mg protein. Pretreatment of the tubules with chloroethylclonidine, 100 microM, reduced the Bmax of [3H]prazosin binding by about 50%, indicating the presence of the alpha 1B-adrenoceptor subtype. Competition studies performed with the alpha-adrenoceptor antagonists, WB 4101, (+)-niguldipine, 5-methylurapidil and phentolamine were shallow and could be distinguished into a high affinity (alpha 1A) and a low affinity site (alpha 1B) with an approximately equal distribution of both receptor subtypes. These observations clearly demonstrate the existence of alpha 1A- and alpha 1B-adrenoceptor subtypes in the renal proximal tubules.
Gopalakrishnan
S M
SM
College of Pharmacy, University of Houston, TX 77204-5515.
Chen
C
C
Lokhandwala
M F
MF
D000317:Adrenergic alpha-Antagonists / Q000378:metabolism*; D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D003000:Clonidine / Q000031:analogs & derivatives / Q000494:pharmacology; D007684:Kidney Tubules / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D011224:Prazosin / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000378:metabolism*
D000317:Adrenergic alpha-Antagonists; D011942:Receptors, Adrenergic, alpha; C051731:chlorethylclonidine; D003000:Clonidine; D011224:Prazosin