Wolffram S, Frischknecht R, Scharrer E
Zentralbl Veterinarmed A. 1989 Dec;36(10):755-62. doi: 10.1111/j.1439-0442.1989.tb00789.x.
Although it is well established that Na and Cl are actively absorbed by the rumen epithelium, nothing is known about the regulation of electrolyte transport across the rumen mucosa. Therefore, we have investigated the influence of theophylline, a known inhibitor of the enzyme phosphodiesterase, on the electrical parameters of the rumen epithelium as well as on electrolyte (Na, Cl, K) transport across this tissue. The experiments were performed using isolated rumen mucosa from sheep mounted in a Ussing type chamber. Serosal addition of theophylline resulted in a significant drop of the transepithelial potential difference as well as the short circuit current. The effect of theophylline is probably mediated by cAMP, since the addition of cAMP yielded qualitatively similar results. With respect to the ion fluxes only transport of Na in the muco-serosal direction and as a result the net flux of Na were significantly reduced in the presence of theophylline. The effects of theophylline on rumen epithelium are best explained by an inhibition of electrogenic as well as electroneutral Na transport. Since cAMP serves as a second messenger for the effect of various regulatory substances including gastrointestinal hormones and transmitters regulation of electrolyte transport across the rumen epithelium possibly occurs under physiological conditions.
虽然已知钠和氯可被瘤胃上皮细胞主动吸收，但对于跨瘤胃黏膜的电解质转运调节却一无所知。因此，我们研究了磷酸二酯酶的已知抑制剂茶碱对瘤胃上皮细胞电参数以及对跨该组织的电解质（钠、氯、钾）转运的影响。实验使用安装在尤斯灌流小室中的绵羊离体瘤胃黏膜进行。在浆膜侧添加茶碱导致跨上皮电位差以及短路电流显著下降。茶碱的作用可能是由环磷酸腺苷（cAMP）介导的，因为添加cAMP产生了定性相似的结果。关于离子通量，仅在存在茶碱的情况下，向黏液 - 浆膜方向的钠转运以及钠的净通量显著降低。茶碱对瘤胃上皮细胞的作用最好用对电生性以及电中性钠转运的抑制来解释。由于cAMP作为包括胃肠激素和递质在内的各种调节物质作用的第二信使，跨瘤胃上皮细胞的电解质转运调节可能在生理条件下发生。
