| Summary: | We studied the secretory phase of fat absorption by sacs of the everted intestine in vitro when long chain fatty acid and monoglyceride had been taken up from a physicochemically defined bile salt micellar solution. After uptake, a sac received a supplemental incubation in a saline solution without added lipid. The presence of calcium ion in the medium during supplemental incubation was essential for the production and release of resynthesized triglyceride in the form of chylomicrons. The particles appeared to enter the serosal fluid via the lacteals. The rate of secretion of the lipid varied directly with the concentration of calcium ion in the mucosal fluid in the range 100-900 microM. At a given concentration in the serosal or mucosal fluid, the calcium ion in the latter fluid had the greater effect. The study of additional factors included the original location of the segment in the intestine of the living animal, temperature, use of D2O instead of water, and the effects of Ba2+, Sr2+, Mg2+, and La3+ on lipid secretion.
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