Regulation of 5-hydroxytryptamine2 (5-HT2) receptor expression in cultured rat aortic smooth muscle cells by SR 46349B, a selective 5-HT2 receptor antagonist.
Regulation of 5-hydroxytryptamine (5-HT2) receptor expression by SR 46349B, a potent and selective 5-HT2 receptor antagonist, was investigated in cultured rat aortic smooth muscle cells. Binding of [3H]SR 46349B to rat vascular smooth muscle cells was time-dependent, reversible, and saturable. [3H]SR 46349B bound to one class of specific binding sites with high affinity (KD = 1.3 +/- 0.3 nM; Bmax = 176 +/- 42 fmol/10(5) cells). Exposure of cells to a 1 microM concentration of the 5-HT2 agonist (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane ((+/-)-DOI) or the antagonist ketanserin led to a significant decrease in 5-HT2 receptor density as measured by [3H]SR 46349B binding. In contrast, exposure of cells to 1 microM SR 46349B caused a marked increase in the maximal binding capacity of [3H]SR 46349B, with a maximal effect at 24 h (73% increase). The affinity constant was not affected by prior exposure to (+/-)-DOI, ketanserin, or SR 46349B. Furthermore, exposure of cells to 1 microM (+/-)-DOI or ketanserin produced, 48 h later, a decrease in the ability of (+/-)-DOI to stimulate phosphoinositide turnover in the cells, whereas treatment with SR 46349B induced a significant stimulation of the 5-HT2 receptor-linked signal transduction. This effect occurred with no changes in the amount of 5-HT2 receptor mRNAs as measured by quantitative polymerase chain reaction. These results indicate that SR 46349B increases 5-HT2 receptor binding and functions without altering steady-state 5-HT2 mRNA levels in cultured rat aortic smooth muscle cells.
Rinaldi-Carmona
M
M
Sanofi Recherche, Montpellier, France.
Prabonnaud
V
V
Bouaboula
M
M
Poinot-Chazel
C
C
Casellas
P
P
Le Fur
G
G
Herbert
J M
JM
D000662:Amphetamines / Q000494:pharmacology; D000818:Animals; D001011:Aorta; D001483:Base Sequence; D001665:Binding Sites; D002478:Cells, Cultured; D017931:DNA Primers; D005464:Fluorobenzenes / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D007650:Ketanserin / Q000494:pharmacology; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010636:Phenols / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D010716:Phosphatidylinositols / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011985:Receptors, Serotonin / Q000235:genetics* / Q000378:metabolism; D012702:Serotonin Antagonists / Q000378:metabolism / Q000494:pharmacology*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology
D000662:Amphetamines; D017931:DNA Primers; D005464:Fluorobenzenes; D010636:Phenols; D010716:Phosphatidylinositols; D012333:RNA, Messenger; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; C076033:SR 46349B; D007650:Ketanserin; C015952:4-iodo-2,5-dimethoxyphenylisopropylamine