ACCUMULATION OF CALCIUM IN LAYING FOWL INTESTINE IN VITRO

Laying hen intestinal tissue was incubated in media containing 45Ca2+, and the accumulation of this isotope was assessed in either the whole tissue or the mucosa. The variable osmotic agent in the medium was mannitol, and the inclusion of any substance was at its expense. The following observations were made: 1. 1. The specific activity ( 45Ca2+ 40Ca2+) of the accumulated Ca2+ was found to be constant. 2. 2. The intestinal accumulation of 45Ca2+ was linearly related to the activity of Ca2+ in the incubation medium. 3. 3. Chelating agents reduced the accumulation to a lesser extent than expected on the basis of Ca2+ activity in the medium, suggesting some accumulation of complexed Ca. 4. 4. More 45Ca2+ was accumulated from the Na+-poor as compared with Na+-rich medium. 5. 5. The accumulation was higher with fructose than with glucose in the medium. Neither ouabain nor phlorizin inhibited the accumulation of 45Ca2+ from an Na+-poor medium. 6. 6. Incubation of intestinal tissue in an Na+-poor medium resulted in an O2 consumption lower than with Na+-rich medium. This effect was reversible after 30 min of incubation. Similarly, the effect of Na+ on the accumulation of 45Ca2+ was reversible after the same time period. 7. 7. The accumulation was linear with respect to the Ca2+ activity of the medium regardless of the Na+ concentration. The findings are consistent with the concept of diffusion as the mechanism for the entry of Ca2+ into the mucosa, although they do not entirely rule out some participation of other types of transport. © 1969.