Kreydiyyeh S I
Department of Biology, Faculty of Arts & Sciences, American University of Beirut, Lebanon.
Life Sci. 2000 Aug 4;67(11):1275-83. doi: 10.1016/s0024-3205(00)00717-7.
The effect of epinephrine on the activity of the Na+-K+ ATPase was studied in isolated rat jejunal cells. The activity of the pump was assessed by measuring the ouabain inhibitable K+ accumulation by the enterocytes using 86Rb as a tracer. Epinephrine stimulated significantly the Na+-K+ ATPase in crypt cells but not in villus cells. This effect was still apparent in presence of propranolol and prazocin but disappeared in presence of yohimbine. Amiloride did not affect the epinephrine-induced stimulation. Calcium channel blockers and dibutyryl cAMP enhanced the activity of the pump, and exerted respectively overlapping and additive effects with epinephrine, when added simultaneously. The calcium ionophore A23187 inhibited the basal activity of the ATPase and the stimulatory effect of epinephrine disappeared in its presence. These results suggest that epinephrine stimulates the Na+-K+ ATPase in jejunal crypt cells by activating alpha2 receptors and decreasing intracellular calcium, and not by altering cAMP levels.
在分离的大鼠空肠细胞中研究了肾上腺素对Na+-K+ ATP酶活性的影响。通过使用86Rb作为示踪剂测量哇巴因可抑制的肠细胞K+积累来评估泵的活性。肾上腺素显著刺激隐窝细胞中的Na+-K+ ATP酶，但对绒毛细胞无此作用。在普萘洛尔和哌唑嗪存在时，这种作用仍然明显，但在育亨宾存在时消失。氨氯地平不影响肾上腺素诱导的刺激作用。钙通道阻滞剂和二丁酰环磷腺苷增强了泵的活性，当同时添加时，它们分别与肾上腺素产生重叠和相加作用。钙离子载体A23187抑制ATP酶的基础活性，且在其存在时肾上腺素的刺激作用消失。这些结果表明，肾上腺素通过激活α2受体和降低细胞内钙来刺激空肠隐窝细胞中的Na+-K+ ATP酶，而不是通过改变环磷腺苷水平。
