EFFECT OF PERIPHERALLY AND CENTRALLY ADMINISTERED CALCITONIN ON GALLBLADDER EMPTYING IN DOGS

The effect of calcitonin on meal-stimulated gallbladder emptying (GEE) was examined after intravenous (i.v.) and intracerebroventricular (i. c.v,) administration in six mongrel dogs. The gallbladder contraction was surveyed by means of real-time ultrasonography in conscious dogs, Calcitonin given i,v, elicited an immediate and strong inhibition of p ostprandial GBE-the integrated 0- to 120-min gallbladder response was 118.1 +/- 8.0%. h after placebo, whereas it was 91.8 +/- 2.1%. h, 59.4 +/- 17.9%. h (P < 0.001), and 14.2 +/- 20.5%. h (P < 0.001) after 3.6 , 18.0, and 90.0 pmol . kg(-1) calcitonin. respectively, After i.c.v, administration (1.8 and 18.0 pmol . kg(-1)), only the higher calcitoni n dose exerted a moderate inhibitory effect on postprandial GEE. The c alcitonin doses required to evoke a 50% inhibition of meal-stimulated GEE were 15- to 10-fold lower after i,v, than i.c.v. application. Peri pherally given calcitonin brought about a dose-dependent increase in t he interdigestive gallbladder volume-the linear regression of the rela tive gallbladder volume versus calcitonin dose was y = 11.60 [In(dose + 1)] + 97.02 (r = 0.864, P < 0.001). Intravenous application of calci tonin did not affect caerulein-induced GEE. The results obtained imply that: (i) calcitonin exerts an inhibitory influence on meal-induced G EE and that this effect is more pronounced after i.v, than after i.c,v , administration, and (ii) peripherally given calcitonin does not inhi bit caerulein-induced gallbladder contraction in the dog.