Effect of adrenal function on gastrointestinal peptide release in experimental cardiac arrest

Pancreatic polypeptide (PP), neurotensin, substance P, and vasoactive intestinal polypeptide (VIP) are peptides that modify various autonomic and neural functions. These substances are secreted into the blood in response to physiologic stimuli affecting the gastrointestinal tract. To determine the effect of adrenal hormones on gastrointestinal peptide release we measured blood levels of PP, VIP, substance P, and neurotensin in adrenalectomized and intact dogs undergoing cardiac arrest and cardiopulmonary resuscitation (CPR), a condition associated with maximal adrenal stimulation. One hour after completion of abdominal surgery consisting of bilateral adrenalectomy or exposure of the adrenal glands (sham operation), ventricular fibrillation was induced in 19 dogs by direct ventricular discharge. Despite marked elevations of plasma epinephrine and norepinephrine, CPR was associated with minimal endocrine gastrointestinal involvement, restricted to increased VIP levels in sham-operated dogs. No specific gastrointestinal peptide response to cardiac arrest was seen in adrenalectomized animals, but their plasma PP and VIP levels were higher than those of sham-operated dogs. Therefore, acute maximal adrenal stimulation is associated with selective VIP release. In addition, the higher level of the vagally controlled plasma PP in adrenalectomized animals suggests a tonic inhibitory effect of adrenal secretions on the release of this peptide.