PHYSIOLOGY OF VOLTAGE DEPENDENT POTASSIUM CHANNELS IN COLONIC MUSCLES

本项目的目标是阐明K+ 通道控制圆形和圆形的电气和机械活动 犬结肠的纵向平滑肌。在预赛中 我们已经发现，以前被称为 “延迟整流”K+电流至少由三个不同的 频道类型。此外，K/ATP通道和钙激活的K+通道 (BK通道)存在于该组织中。 (1)我们将检验这样一个假设，即电活动的多样性 胃肠道的模式是由于 这些K+通道的类型和表达。因此，我们将确定 “延迟整流”的药理和动力学性质 电压钳制结肠肌细胞及其单通道的组成 细胞贴附和切除的膜贴片的性质。这些数据 将是将克隆和克隆的分子生物学研究联系起来的关键 在完整的组织中观察到K+通道的表达。戈伦霍芬 根据平滑肌组织的电学特性对其进行分类 阶段性(尖峰型和非尖峰型)和强直型的活动模式 肌肉。我们的实验将集中在呈现模型的组织上 这三类中的每一类：我们将利用在 环层结肠肌细胞(时相、非尖峰平滑肌)至 探讨K+通道的类型和相对表达水平。 纵层结肠肌细胞(时相，峰状肌)和 下食道括约肌(紧张性平滑肌)。 (2)我们将研究参与一氧化氮的K+电导和 β-肾上腺素能介导的结肠肌肉松弛。对两个人都是 在这些抑制性神经递质中，已有证据表明 组织水平认为K+通道的激活对膜是必不可少的 超极化和随后的肌肉松弛。但是，该类型的 参与这两个动作的K+通道尚不清楚。我们会 研究循环中确定的K+通道类型的调节 CAMP和cGMP介导的血管平滑肌细胞与蛋白激酶 C.单渠道研究将阐明这些调控的机制 小路。 这些研究将促进我们对电的机制的了解。 以及胃肠道的机械节律性。

The goal of this Project is to clarify the mechanisms by which K+ channels control the electrical and mechanical activity of circular and longitudinal smooth muscle of the canine colon. In preliminary experiments we have found that what previously has been denoted as "delayed rectifier" K+ current is composed of at least three distinct channel types. In addition K/ATP channels and Ca2+-activated K+ channels (BK channels) are present in this tissue. (1) We will test the hypothesis that the diversity of electrical activity patterns in the gastrointestinal tract is due to regional differences in type and expression of these K+ channels. Accordingly, we will determine the pharmacological and kinetic properties of "delayed rectifier" components in voltage clamped colonic myocytes and their single channel properties in cell-attached and excised membrane patches. These data will be essential to link molecular biology studies of cloned and expressed K+ channels to observations in the intact tissue. Golenhofen has classified smooth muscle tissues according to their electrical activity patterns in phasic (spiking and non-spiking types) and tonic muscles. Our experiments will focus on tissues that present models of each of these three classes: We will utilize the protocols developed on circular layer colonic myocytes (phasic, non-spiking smooth muscle) to investigate the types and relative expression levels of K+ channels in longitudinal layer colonic myocytes (phasic, spiking smooth muscle) and the lower esophageal sphincter (tonic smooth muscle). (2) We will investigate the K+ conductances involved in nitric oxide and Beta-adrenergic mediated relaxation of the colonic musculature. For both of these inhibitory neurotransmitters evidence has been obtained on the tissue level that activation of K+ channels is essential for the membrane hyperpolarization and subsequent muscle relaxation. However the type of K+ channel involved in either of these actions is not known. We will investigate regulation of the K+ channel types identified in circular smooth muscle cells by cAMP and cGMP mediated pathways and protein kinase C. Single channel studies will clarify the mechanism of these regulatory pathways. These studies will advance our knowledge of the mechanisms of electrical and mechanical rhythmicity in the gastrointestinal tract.