Cholesterol absorption was studied from the aspect of the obligatory func-tion of bile in the rat.
Bile fistula rats were fed various bile salts with 0.2 μc of cholesterol-4-
14C, 50mg of nonradioactive cholesterol and 0.33ml of oleic acid mixed with a fat and sterol free synthetic basal diet. The following recoveries of radioactivity in the bile were obtained: Na-cholate, 21%; Na-taurocholate, 45%; Na-glyco-cholate, 41%; Na-deoxycholate, 3.5%; and, no more than a trace with lithocholate, chenodeoxycholate, hyodeoxycholate, hyocholate, apocholate, dehydrocholate, and 3α, 12α-dihydroxy-7-keto-cholanate. When taurocholate was fed with dehydrocho-late, a 48% recovery was obtained. When the oleic acid was omitted, the per-centage recovery was reduced to 6% with Na-cholate and 17% with Na-taurocholate.
The absorbability of squalene was compared with that of cholesterol in the intact rat by using the balance method. Forty-four per cent of 61.5mg of squalene and 58% of 50mg of cholesterol were absorbed or not recovered in the feces. The simultaneous feeding of squalene and cholesterol resulted in ap-proximately the same amount, namely, 42% and 54% absorption of squalene and cholesterol, respectively.
In bile fistula rats, only 5.6% of squalene was unrecovered in the feces, while feeding Na-taurocholate with squalene raised this figure to 25% when for cholesterol it was 35%.
Practically no squalane was absorbed by the intestine of intact rats.
It is concluded that cholesterol absorption requires bile acid salts which posses 7α and 12α hydroxyl groups simultaneously in addition to the 3α hydroxyl group in the bile acid molecule.
The requirement of specific bile salts in the absorption of cholesterol may involve the interaction between the bile salt and the cellular substances.
The mechanism for the absorption of cholesterol is tentatively described as a diffusion through a lipoid sieve mediated specifically by cholate or its con-jugates.
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