Centrally mediated stimulation of jejunal water and electrolyte secretion by calcitonin in dogs

Abstract

The effects of intracerebroventricular versus intravenous injection of salmon calcitonin (sCT) at a dose of 0.2 IU X kg-1 on jejunal fluxes of water, Na+, and K+ were investigated before and after vagotomy or an intravenous treatment with indomethacin (1 mg X kg-1) in dogs prepared with a jejunal Thiry-Vella loop. Intestinal transport in the Thiry-Vella loop and concomitant mean transit time were measured during an infusion (2 ml X min-1) of an isotonic electrolyte solution and phenol red bolus injections. Basal net water absorption was significantly (P less than 0.01) reduced by 51.7% from 2 to 3 h after intracerebroventricular administration of sCT, Na+ absorption was reduced by 62.6%, and net flux of K+ was reversed from absorption to secretion. A similar intravenous dose had no effect. Previous treatment with indomethacin or bilateral thoracic vagotomy did not reduce the water, Na+, and K+ secretory effects of centrally administered sCT, whereas indomethacin per se appeared to reduce water and electrolyte absorption. A significant (P less than or equal to 0.05) increase in mean transit time was observed after intracerebroventricular but not intravenous calcitonin (0.2 IU X kg-1), and this effect was abolished after vagotomy. These results suggest that calcitonin may be involved in the central control of intestinal secretion in dog, inasmuch as these effects were mediated by different structures from those affecting intestinal motility.