gastrins and Tachycardia

Pythons exhibit a doubling of heart rate when metabolism increases several times during digestion. Pythons, therefore, represent a promising model organism to study autonomic cardiovascular regulation during the postprandial state, and previous studies show that the postprandial tachycardia is governed by a release of vagal tone as well as a pronounced stimulation from nonadrenergic, noncholinergic (NANC) factors. Here we show that infusion of plasma from digesting donor pythons elicit a marked tachycardia in fasting snakes, demonstrating that the NANC factor resides in the blood. Injections of the gastrin and cholecystokinin receptor antagonist proglumide had no effect on double-blocked heart rate or blood pressure. Histamine has been recognized as a NANC factor in the early postprandial period in pythons, but the mechanism of its release has not been identified. Mast cells represent the largest repository of histamine in vertebrates, and it has been speculated that mast cells release histamine during digestion. Treatment with the mast cell stabilizer cromolyn significantly reduced postprandial heart rate in pythons compared with an untreated group but did not affect double-blocked heart rate. While this study indicates that histamine induces postprandial tachycardia in pythons, its release during digestion is not stimulated by gastrin or cholecystokinin nor is its release from mast cells a stimulant of postprandial tachycardia.

Topics: Animals; Blood Pressure; Boidae; Cromolyn Sodium; Digestion; Gastrins; Heart Rate; Histamine; Histamine Antagonists; Mast Cells; Models, Animal; Postprandial Period; Proglumide; Receptors, Cholecystokinin; Tachycardia

The mechanism for secretin-induced gastrin release in the Zollinger-Ellison syndrome is uncertain. We evaluated whether the stimulatory effect of intravenous secretin on gastrin release was partly mediated through a beta-adrenergic stimulatory mechanism. Serum gastrin concentrations and heart rate were monitored in six patients with the Zollinger-Ellison syndrome. Secretin (2 clinical units/kg) increased mean serum gastrin concentrations from 1558 pg/ml basally to a peak of 3683 pg/ml (136% above baseline). This increase was not altered by pretreatment with 2 mg of propranolol intravenously, a dose which in previous studies blocked terbutaline-induced gastrin release. Secretin increased heart rate by 14 beats/min (20% above base-line) and this also was not altered by propranolol pretreatment. Thus, the stimulatory effects of secretin on gastrinoma cells and the heart do not appear to be mediated by beta-adrenergic receptors.

Topics: Adult; Aged; Gastrins; Heart Rate; Humans; Male; Middle Aged; Propranolol; Radioimmunoassay; Secretin; Tachycardia; Zollinger-Ellison Syndrome

Topics: Adult; Aged; Chronic Disease; Dumping Syndrome; Duodenal Ulcer; Female; Gastrectomy; Gastric Juice; Gastrins; Gastroscopy; Humans; Hypotension; Male; Middle Aged; Pain, Postoperative; Pentagastrin; Postgastrectomy Syndromes; Pyloric Antrum; Pylorus; Radiography; Stomach; Stomach Ulcer; Tachycardia; Vomiting