Identification of alpha 1L-adrenoceptor in mice and its abolition by alpha 1A-adrenoceptor gene knockout.
OBJECTIVE
The alpha(1L)-adrenoceptor has pharmacological properties that distinguish it from three classical alpha(1)-adrenoceptors (alpha(1A), alpha(1B) and alpha(1D)). The purpose of this was to identify alpha(1L)-adrenoceptors in mice and to examine their relationship to classical alpha(1)-adrenoceptors.


METHODS
Radioligand binding and functional bioassay experiments were performed on the cerebral cortex, vas deferens and prostate of wild-type (WT) and alpha(1A)-, alpha(1B)- and alpha(1D)-adrenoceptor gene knockout (AKO, BKO and DKO) mice.


RESULTS
The radioligand [(3)H]-silodosin bound to intact segments of the cerebral cortex, vas deferens and prostate of WT, BKO and DKO but not of AKO mice. The binding sites were composed of two components with high and low affinities for prazosin or RS-17053, indicating the pharmacological profiles of alpha(1A)-adrenoceptors and alpha(1L)-adrenoceptors. In membrane preparations of WT mouse cortex, however, [(3)H]-silodosin bound to a single population of prazosin high-affinity sites, suggesting the presence of alpha(1A)-adrenoceptors alone. In contrast, [(3)H]-prazosin bound to two components having alpha(1A)-adrenoceptor and alpha(1B)-adrenoceptor profiles in intact segments of WT and DKO mouse cortices, but AKO mice lacked alpha(1A)-adrenoceptor profiles and BKO mice lacked alpha(1B)-adrenoceptor profiles. Noradrenaline produced contractions through alpha(1L)-adrenoceptors with low affinity for prazosin in the vas deferens and prostate of WT, BKO and DKO mice. However, the contractions were abolished or markedly attenuated in AKO mice.


CONCLUSIONS
alpha(1L)-Adrenoceptors were identified as binding and functional entities in WT, BKO and DKO mice but not in AKO mice, suggesting that the alpha(1L)-adrenoceptor is one phenotype derived from the alpha(1A)-adrenoceptor gene.
Muramatsu
I
I
Division of Pharmacology, Department of Biochemistry and Bioinformative Sciences, University of Fukui School of Medicine, Eiheiji, Fukui, Japan. muramatu@u-fukui.ac.jp
Morishima
S
S
Suzuki
F
F
Yoshiki
H
H
Anisuzzaman
A S M
AS
Tanaka
T
T
Rodrigo
M C
MC
Myagmar
B E
BE
Simpson
P C
PC
D000818:Animals; D002540:Cerebral Cortex / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D007211:Indoles / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009119:Muscle Contraction; D009638:Norepinephrine / Q000494:pharmacology; D011224:Prazosin / Q000378:metabolism; D011467:Prostate / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D011869:Radioligand Assay; D018340:Receptors, Adrenergic, alpha-1 / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D013449:Sulfonamides / Q000378:metabolism; D000077409:Tamsulosin; D014316:Tritium; D014649:Vas Deferens / Q000187:drug effects / Q000378:metabolism / Q000502:physiology
D007211:Indoles; C099495:RS 17053; D018340:Receptors, Adrenergic, alpha-1; D013449:Sulfonamides; D014316:Tritium; C095285:silodosin; D000077409:Tamsulosin; D009638:Norepinephrine; D011224:Prazosin