Meuth-Metzinger Valérie Le, Philouze-Rome Véronique, Metzinger Laurent, Gespach Christian, Guilloteau Paul
Université Paris 13, Faculté de Médecine, Laboratoire de Pharmacologie Expérimentale et Clinique, Bobigny CEDEX, France.
Pancreas. 2005 Aug;31(2):174-81. doi: 10.1097/01.mpa.0000174938.89815.e9.
Secretin is a key regulator of pancreatic secretion, but the molecular basis of its action is not well understood, especially in the calf pancreas. Our study investigated the expression and functional competence of secretin receptors (SEC-R) in calf pancreatic membranes.
We used reverse transcriptase-polymerase chain reaction, sequencing, and Northern blot to assess the expression of the SEC-R gene. The functional characterization of SEC-R was accomplished using adenylate cyclase (AC) assay.
We successfully amplified, by reverse transcriptase-polymerase chain reaction, a fragment of the SEC-R gene from 119-day-old calf pancreas. This sequence shows higher homology with SEC-R than with vasoactive intestinal polypeptide (VIP)-1 and VIP-2 receptors from other species. Northern blot analysis detected a 1.8-kb transcript. Accordingly, secretin stimulates AC activity in calf pancreatic membranes isolated from 28- and 119-day-old animals with a potency (Ka) of 1.9 to 2.7 nmol/L. Maximal AC stimulation induced by secretin represented a 3- to 4-fold increase of basal activity. AC activation by secretin was inhibited by the 2 SEC-R antagonists, [psi4,5] secretin (l micromol/L) and [5-27] secretin (10 micromol/L). Interestingly, [psi4,5] secretin was ineffective against VIP-induced AC stimulation.
Our data indicate that secretin exerts a direct action on pancreatic secretion through specific SEC-R coupled to the AC system. Calf pancreatic SEC-Rs are coexpressed with VIP-2 receptors that we previously identified by ligand binding and cross-linking experiments.
促胰液素是胰腺分泌的关键调节因子，但其作用的分子基础尚未完全明确，尤其是在犊牛胰腺中。我们的研究调查了促胰液素受体（SEC-R）在犊牛胰腺膜中的表达及功能活性。
我们采用逆转录-聚合酶链反应、测序及Northern印迹法评估SEC-R基因的表达。通过腺苷酸环化酶（AC）测定完成SEC-R的功能特性分析。
我们通过逆转录-聚合酶链反应成功从119日龄犊牛胰腺中扩增出SEC-R基因片段。该序列与SEC-R的同源性高于其他物种的血管活性肠肽（VIP）-1和VIP-2受体。Northern印迹分析检测到一条1.8 kb的转录本。相应地，促胰液素刺激从28日龄和119日龄动物分离的犊牛胰腺膜中的AC活性，效力（Ka）为1.9至2.7 nmol/L。促胰液素诱导的最大AC刺激代表基础活性增加3至4倍。促胰液素对AC的激活被两种SEC-R拮抗剂[psi4,5]促胰液素（1 μmol/L）和[5-27]促胰液素（10 μmol/L）抑制。有趣的是，[psi4,5]促胰液素对VIP诱导的AC刺激无效。
我们的数据表明促胰液素通过与AC系统偶联的特异性SEC-R对胰腺分泌发挥直接作用。犊牛胰腺SEC-R与我们之前通过配体结合和交联实验鉴定的VIP-2受体共表达。
