PMID- 10052015
OWN - NLM
STAT- MEDLINE
DCOM- 19990429
LR  - 20131121
IS  - 0300-9831 (Print)
IS  - 0300-9831 (Linking)
VI  - 69
IP  - 1
DP  - 1999 Jan
TI  - Studies on the effect of dose size on the absorption of beta-carotene by the rat 
      in vivo.
PG  - 8-15
AB  - This study was carried out to choose between two hypotheses with respect to the 
      regulation of beta-carotene (BC) conversion to retinol in the whole animal: 
      uptake of BC into intestinal mucosa is limited by saturation of an intestinal 
      receptor; or the conversion to retinol is limited by saturation of the conversion 
      enzyme(s). Groups of rats were given five different dose levels of labeled BC by 
      stomach tube. Labeled and total BC and retinol were isolated from tissues and 
      intestinal contents after 4 h. Results showed a positive linear relationship 
      between BC in the intestinal wall and the dose administered, with no saturation 
      level up to 1440 micrograms administered. Per cent formation of newly formed 
      retinol from newly absorbed (i.e., labeled) BC was 20-26% of the three lower dose 
      groups, 10% for the highest dose. No retinyl esters could be detected in the 
      intestine. Most of the administered BC was in the intestinal contents, about 
      100-times more than in the intestinal wall and mucosa. Newly formed retinol in 
      plasma was about 10-times that in liver. Small amounts of newly absorbed BC were 
      found in liver, but no labeled retinyl esters. These results suggest that the 
      absorption of BC is very inefficient; that it does not occur through an 
      intestinal receptor; that the formation of retinol is regulated at the level of 
      the conversion enzyme(s).
FAU - Chen, Y H
AU  - Chen YH
AD  - Graduate Institute of Nutrition and Health Science, Taipei Medical College, 
      Taiwan, R.O.C.
FAU - Oace, S M
AU  - Oace SM
FAU - Wolf, G
AU  - Wolf G
LA  - eng
PT  - Journal Article
PL  - Switzerland
TA  - Int J Vitam Nutr Res
JT  - International journal for vitamin and nutrition research. Internationale 
      Zeitschrift fur Vitamin- und Ernahrungsforschung. Journal international de 
      vitaminologie et de nutrition
JID - 1273304
RN  - 01YAE03M7J (beta Carotene)
RN  - 11103-57-4 (Vitamin A)
SB  - IM
MH  - Animals
MH  - Chromatography, High Pressure Liquid
MH  - Dose-Response Relationship, Drug
MH  - Esterification
MH  - Intestinal Absorption
MH  - Intestinal Mucosa/metabolism
MH  - Intestine, Small/metabolism
MH  - Intubation, Gastrointestinal
MH  - Liver/metabolism
MH  - Male
MH  - Rats
MH  - Rats, Sprague-Dawley
MH  - Vitamin A/blood/metabolism
MH  - beta Carotene/*administration & dosage/blood/*pharmacokinetics
EDAT- 1999/03/03 00:00
MHDA- 1999/03/03 00:01
CRDT- 1999/03/03 00:00
PHST- 1999/03/03 00:00 [pubmed]
PHST- 1999/03/03 00:01 [medline]
PHST- 1999/03/03 00:00 [entrez]
AID - 10.1024/0300-9831.69.1.8 [doi]
PST - ppublish
SO  - Int J Vitam Nutr Res. 1999 Jan;69(1):8-15. doi: 10.1024/0300-9831.69.1.8.