ISSN:
1432-2013
Keywords:
Key words l-Alanine
;
l-Glutamate
;
Transport
;
Sarcolemma
;
Myocardial protection
;
Heart cells
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract During cardiac insults, heart cells synthesise and accumulate alanine as a part of the anaerobic energy production pathway. The transport of alanine presumably influences this pathway, making it important to characterise the l-alanine transporter in the heart. In this study, we have investigated the transport of l-alanine across the sarcolemma using a novel approach, namely utilisation of two preparations: cardiac sarcolemmal vesicles and cardiac myocytes. Both preparations were isolated from the heart of the same mammalian species. l-Alanine uptake in both preparations was sodium dependent. In the sarcolemmal vesicles, the sodium dependent component was electrogenic and saturated with an estimated Michaelis-Menten constant (K m) and maximal reaction velocity (V max) of 0.48±0.18 mM and 279.97±64.17 pmol/mg per min respectively at room temperature. In the isolated myocytes, l-alanine uptake was linear in sodium-containing media, with an estimated K m and V max of 9.65±0.76 mM and 169.81±13.22 pmol/µl per min respectively at 10°C for the sodium-dependent component. Inhibition of cotransport by a variety of substrates indicated that l-alanine uptake in the heart is mediated by an A- or ASC-like system. These characteristics of l-alanine transport suggest that under ischaemic conditions, l-alanine efflux will be activated, thus allowing for the continuous utilisation of other amino acids for energy production.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004240050647
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