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Myocardial carnitine transport.
N Siliprandi1, M Ciman, L Sartorelli
1Institute of Biological Chemistry, University of Padova, Italy.
Basic Research in Cardiology
|January 1, 1987
Summary
Mammals synthesize carnitine in specific organs, relying on blood uptake for other tissues. This study reveals a crucial carnitine-deoxycarnitine exchange mechanism between organs, essential for carnitine transport and utilization.
Area of Science:
- Biochemistry
- Physiology
- Metabolic Transport
Background:
- Carnitine synthesis occurs in the liver, brain, and kidneys from trimethyllysine.
- Most tissues lack the final hydroxylase enzyme, necessitating carnitine uptake from circulation.
- Interorgan transport of carnitine, precursors, and derivatives is vital for cellular energy metabolism.
Purpose of the Study:
- To describe the interorgan transport of carnitine and its derivatives.
- To investigate the bidirectional exchange of carnitine and deoxycarnitine across cardiac sarcolemma.
- To elucidate the physiological mechanism of carnitine-deoxycarnitine exchange in mammals.
Main Methods:
- In vitro studies using heart slices to analyze carnitine-deoxycarnitine exchange.
- In vivo experiments in rats involving administration of carnitine or deoxycarnitine.
- Measurement of carnitine and deoxycarnitine levels in tissues and urine.
Main Results:
- Demonstrated a 1:1 bidirectional exchange between carnitine and deoxycarnitine across cardiac sarcolemma.
- The exchange was insensitive to metabolic inhibitors but sensitive to thiol reagents.
- In vivo studies confirmed that carnitine administration displaces deoxycarnitine and vice versa.
Conclusions:
- Evidence supports an interorgan transport system involving carnitine and deoxycarnitine.
- Deoxycarnitine released from muscles is hydroxylated to carnitine in the liver/kidneys and returned to muscles.
- This carnitine-deoxycarnitine exchange is a key mechanism for maintaining carnitine homeostasis.