Quantitative aspects of the effect of somatostatin on bile flow in the rat [proceedings].

Glycoprotein concentrations (0) were measured by a modification of the method of Mantle & Allen (1978). Viscosities were measured with an Ostwald viscometer at 25OC within 5min of collection of samples in order to minimize the observed fall in viscosity due to peptic action. Specific (v,,,, 0) and reduced specific viscosities (vred., A) are illustrated. Each point is an observation on a pooled sample from six cats. protein polymer to degraded subunit was much greater than in low-viscosity samples during infusion of pentagastrin alone. Over a period of time, endogenous pepsin split the glycoprotein polymer into subunits, and this was accompanied by a decrease in the viscosity of the juice. The increased viscosity with secretin infusion cannot be explained by a decrease in pepsin activity, since this doubled during the secretin infusion: also, the viscosity contribution from the pepsin was negligible. In conclusion, the mucus glycoprotein seen on infusion with pentagastrin alone is associated with predominately degraded glycoprotein subunits, and a low viscosity. This probably reflects the extra volume of gastric juice washing out previously degraded mucus from the stomach. With secretin, however, there is a large rise in the reduced and specific viscosity, and in the undegraded polymeric glycoprotein characteristic of the gel. This rise in undegraded glycoprotein in the juice, assuming no increase in mechanical erosion, is compatible with a genuine increase in mucus-gel secretion stimulated by secretin. These results also emphasize that measurements of the glycoprotein concentration or output in gastric juice alone cannot be directly equated with changes in the amount of the surface mucus gel.