A multicompartmental model of vitamin A kinetics in rats with marginal liver vitamin A stores

Michael Henry Green, L. Uhl, J. B. Green

Research output: Contribution to journalArticle

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Abstract

A linear, first-order, constant-coefficient multicompartmental model is presented which describes the dynamics of [3H]retinol turnover in adult rats with normal plasma retinol concentrations but low liver stores (<100 μg of retinol equivalents). To fit plasma and tissue (liver, kidney, and rest of carcass) tracer and tracee data, eight physiological compartments were required in the model: two in plasma (proposed to correspond to the retinol transport complex, and retinyl esters in plasma lipoproteins) and two each in liver, kidneys, and other extrahepatic tissues. Extensive recycling of retinol among plasma, liver, and the rest of carcass was also required. The model predicted that 44% of whole body vitamin A (143 μg) was in extrahepatic tissues. The vitamin A utilization rate (system disposal rate) was 6.9 μg of retinol equivalents/day. The system residence time (mean sojourn time) for vitamin A was 21 days, and the fractional catabolic rate for the system was 5%/day. The mean transit time (turnover time) for vitamin A in its plasma retinol transport complex was 0.078 days (1.9 hr); the residence time was 0.98 day, versus 11 days in the liver, 9 days in carcass, and 0.54 days in kidneys. The model predicted that, of the plasma turnover, 48% recycled to the liver and 52% to extrahepatic tissues. The liver retinol secretion rate was 48 μg/day, more than half of which was from recycled plasma retinol. Since the plasma retinol turnover rate (87 μg/day) was 13 times the system disposal rate, the data suggest that this is a high response system in which changes in the dynamics of recycling of retinol allow for rapid adjustment in vitamin A distribution in response to changes in nutritional, metabolic, or physiological conditions; and in which plasma retinol levels are controlled homeokinetically by changes in hepatic and extrahepatic recycling of holo retinol-binding protein.

Original languageEnglish (US)
Pages (from-to)806-818
Number of pages13
JournalJournal of Lipid Research
Volume26
Issue number7
StatePublished - Jan 1 1985

Fingerprint

Vitamin A
Liver
Rats
Kinetics
Plasmas
Recycling
Tissue
Kidney
Retinol-Binding Proteins
Lipoproteins

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Endocrinology
  • Cell Biology

Cite this

Green, Michael Henry ; Uhl, L. ; Green, J. B. / A multicompartmental model of vitamin A kinetics in rats with marginal liver vitamin A stores. In: Journal of Lipid Research. 1985 ; Vol. 26, No. 7. pp. 806-818.
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abstract = "A linear, first-order, constant-coefficient multicompartmental model is presented which describes the dynamics of [3H]retinol turnover in adult rats with normal plasma retinol concentrations but low liver stores (<100 μg of retinol equivalents). To fit plasma and tissue (liver, kidney, and rest of carcass) tracer and tracee data, eight physiological compartments were required in the model: two in plasma (proposed to correspond to the retinol transport complex, and retinyl esters in plasma lipoproteins) and two each in liver, kidneys, and other extrahepatic tissues. Extensive recycling of retinol among plasma, liver, and the rest of carcass was also required. The model predicted that 44{\%} of whole body vitamin A (143 μg) was in extrahepatic tissues. The vitamin A utilization rate (system disposal rate) was 6.9 μg of retinol equivalents/day. The system residence time (mean sojourn time) for vitamin A was 21 days, and the fractional catabolic rate for the system was 5{\%}/day. The mean transit time (turnover time) for vitamin A in its plasma retinol transport complex was 0.078 days (1.9 hr); the residence time was 0.98 day, versus 11 days in the liver, 9 days in carcass, and 0.54 days in kidneys. The model predicted that, of the plasma turnover, 48{\%} recycled to the liver and 52{\%} to extrahepatic tissues. The liver retinol secretion rate was 48 μg/day, more than half of which was from recycled plasma retinol. Since the plasma retinol turnover rate (87 μg/day) was 13 times the system disposal rate, the data suggest that this is a high response system in which changes in the dynamics of recycling of retinol allow for rapid adjustment in vitamin A distribution in response to changes in nutritional, metabolic, or physiological conditions; and in which plasma retinol levels are controlled homeokinetically by changes in hepatic and extrahepatic recycling of holo retinol-binding protein.",
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A multicompartmental model of vitamin A kinetics in rats with marginal liver vitamin A stores. / Green, Michael Henry; Uhl, L.; Green, J. B.

In: Journal of Lipid Research, Vol. 26, No. 7, 01.01.1985, p. 806-818.

Research output: Contribution to journalArticle

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