Rogines-Velo María Pía, Pelorosso Facundo Germán, Zold Camila Lidia, Nowak Wanda, Pesce Guido Oscar, Sardi Sergio Pablo, Brodsky Paula Tamara, Rothlin Rodolfo Pedro
Departamento de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155, Piso 9, CP 1121, Buenos Aires, Argentina.
Naunyn Schmiedebergs Arch Pharmacol. 2002 Dec;366(6):587-95. doi: 10.1007/s00210-002-0636-9. Epub 2002 Sep 27.
This study attempted to characterize pharmacologically the involvement of 5-HT(2A) receptors in 5-HT-induced contractile responses in human umbilical vein (HUV) rings employing functional and radioligand binding assays. In HUV rings, prazosin 1 micro M did not affect contractile responses elicited by 5-HT, ruling out the involvement of alpha(1)-adrenoceptors in contractile responses to 5-HT. 5-HT-induced contractions were competitively blocked by ketanserin, a 5-HT(2A)-selective antagonist. The apparent pA(2) value was 9.8 and the Schild slope significantly less than unity, suggesting that 5-HT-induced responses are mediated by a heterogeneous receptor population. Alpha-methyl-5-HT, a selective 5-HT(2) receptor agonist, induced contractions that were antagonized in a competitive manner by ketanserin. The slope regression was not significantly different from unity and the pA(2) value was 8.8. The selective 5-HT(2A) ligand spiperone produced a parallel rightward shift on 5-HT CRCs in HUV rings. The calculated pA(2) was 9.0, which is in accord for an interaction with the 5-HT(2A) receptor subtype. Alpha-methyl-5-HT CRCs were competitively blocked by spiperone treatment. The Schild analysis yielded a pA(2) of 9.1 with a slope not significantly different from unity. The 5-HT(2C/2A) antagonist mesulergine 10 nM did not affect 5-HT CRCs, suggesting that 5-HT(2C) receptors are not involved in 5-HT-elicited contractions. Higher concentrations of mesulergine showed a parallel rightward shift on 5-HT responses. The calculated pA(2) was 7.44, which suggests an interaction with the 5-HT(2A) receptor subtype. In addition, mesulergine competitively blocked alpha-methyl-5-HT CRCs. The Schild slope was not significantly different from unity and the p A(2) value was 7.98. The binding of [(3)H]ketanserin to HUV membranes was saturable and of high affinity. Ketanserin displayed a monophasic curve which was best fit with a single component of binding. Nonlinear least squares analysis of the binding curves revealed a high affinity K(d) of 0.30 nM and a B(max) of 134 fmol/mg protein. These findings provide strong pharmacological evidence of the involvement of 5-HT(2A) receptors in 5-HT-induced vasoconstriction in HUV. In addition, the contribution of another receptor population cannot be excluded. The results also suggest that this receptor population is neither an alpha(1)-adrenoceptor nor a 5-HT(2C) receptor subtype.
本研究试图通过功能和放射性配体结合试验，从药理学角度表征5-羟色胺（5-HT）诱导人脐静脉（HUV）环收缩反应过程中5-HT（2A）受体的作用。在HUV环中，1微摩尔的哌唑嗪不影响5-HT引起的收缩反应，排除了α（1）-肾上腺素能受体参与5-HT收缩反应的可能性。5-HT诱导的收缩被5-HT（2A）选择性拮抗剂酮色林竞争性阻断。表观pA（2）值为9.8，Schild斜率显著小于1，表明5-HT诱导的反应由异质性受体群体介导。α-甲基-5-HT是一种选择性5-HT（2）受体激动剂，其诱导的收缩被酮色林竞争性拮抗。斜率回归与1无显著差异，pA（2）值为8.8。选择性5-HT（2A）配体螺哌隆使HUV环中5-HT的累积剂量-反应曲线（CRCs）平行右移。计算得到的pA（2）为9.0，这与与5-HT（2A）受体亚型相互作用相符。螺哌隆处理竞争性阻断了α-甲基-5-HT的CRCs。Schild分析得到的pA（2）为9.1，斜率与1无显著差异。10纳摩尔的5-HT（2C/2A）拮抗剂美舒麦角不影响5-HT的CRCs，表明5-HT（2C）受体不参与5-HT诱导的收缩。更高浓度的美舒麦角使5-HT反应平行右移。计算得到的pA（2）为7.44，表明与5-HT（2A）受体亚型相互作用。此外，美舒麦角竞争性阻断α-甲基-5-HT的CRCs。Schild斜率与1无显著差异，pA（2）值为7.98。[（3）H]酮色林与HUV膜的结合具有饱和性和高亲和力。酮色林呈现单相曲线，最适合用单一结合成分拟合。结合曲线的非线性最小二乘法分析显示，高亲和力K（d）为0.30纳摩尔，B（max）为134飞摩尔/毫克蛋白。这些发现提供了强有力的药理学证据，证明5-HT（2A）受体参与了HUV中5-HT诱导的血管收缩。此外，不能排除另一种受体群体的作用。结果还表明，该受体群体既不是α（1）-肾上腺素能受体，也不是5-HT（2C）受体亚型。
