Measurement of the receptor turnover using an irreversible inactivating method. Theoretical assumptions, limitations...

Recently it has become possible to characterize turnover of different receptors using the irreversible receptor inactivating agent N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ). The mechanism of the EEDQ-evoked inactivation is due to creation of highly reactive mixed carbonic anhydrides from carboxyl groups, which react with a sterically accessible nucleophilic groups (e.g. free alpha-amino groups) of receptor peptides. The aim of this review is to describe basic theoretical and practical analyses in the receptor turnover measurement. The synthesis and degradation of receptors were shown as zero-order and first-order processes, respectively. Having made the above assumption it is very simple to characterize the receptor turnover in a culture tissue. However, a more complicated situation arises when EEDQ is used to assess an "ex vivo" (in vivo) receptor turnover. Furthermore, details which emerge during an analysis of the results of "ex vivo" receptor turnover measurements are discussed.