AJP - Gastrointestinal and Liver Physiology, Vol 249, Issue 3 399-G407, Copyright © 1985 by American Physiological Society
Dietary fat assimilation and bile salt absorption in the killifish intestine
R. E. Honkanen, M. W. Rigler and J. S. Patton
Radiolabeled taurocholate (TC) and triolein were used to study fat
assimilation and bile salt absorption in the stomachless saltwater
killifish, Fundulus heteroclitus. Fat absorption occurred primarily in the
proximal intestine with approximately 87% of a single dose (9 mg fat/8 g
fish) absorbed in 2 h. Luminal triolein hydrolysis and enterocyte triolein
resynthesis were tightly coupled. Killifish gallbladder bile contains
taurocholate and cholate in an equal molar ratio at a combined
concentration of 237 +/- 25 mM (n = 10) in 24-h-fasted fish. During fat
assimilation luminal bile salt and fatty acid concentrations ranged between
10 and 30 mM. Between and during meals the total concentration of bile
salts in the intestinal tissue remained roughly constant (4-6 mM) with the
proximal one-third of the intestine containing 40% of the total and the
remainder equally distributed between the mid and distal regions. All three
regions of the intestine rapidly incorporated ingested TC in vivo, with the
amount incorporated proportional to the pool size. In contrast, in vitro at
low TC concentrations (60 nM), the distal one-third of the intestine
incorporated 10 times as much TC in 2-min uptake experiments as the
proximal and mid regions. Although there are many similarities between fat
and bile salt assimilation in killifish and mammals, overall the processes
are much simpler in killifish.
