In vivo and in vitro influence of human recombinant hemoglobin on esophageal function

The purpose of the present investigation was to examine the influence of a nitric oxide scavenger, hemoglobin (Hb), on esophageal function. Intraluminal pressures of anesthetized opossums were recorded from lower esophageal sphincter (LES) and 1, 5, and 9 cm above the LES. The influence of a representative Hb-based oxygen carrier was examined on swallowing-induced esophageal peristalsis and LES relaxation. In in vitro studies, LES relaxation and esophageal peristaltic contractions were induced by the activation of nonadrenergic noncholinergic (NANC) neurons by electrical field stimulation (EFS). Hb caused significant impairment in swallowing- and EFS-induced LES relaxation and a significant increase in the speed of esophageal peristalsis. In some experiments, swallowing caused simultaneous contractions in the esophagus following Hb administration. Although Hb completely blocked LES relaxation by NO and significantly attenuated that by NANC nerve stimulation, it had no significant effect on isoproterenol-induced LES relaxations. The data support the role of NO in LES relaxation and esophageal peristalsis. This esophageal model may be important in understanding the influence of NO inhibitors and scavengers in gastrointestinal motility.