PubMed · 5492806
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G A Gilbert. 1970. Mixed haemoglobin molecules.. https://doi.org/10.1042/bj1190032p
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The influence of palmitic acid, 13-cis-retinoic acid, all-trans-retinoic acid, and all-trans-retinol on the activity of the human cholesteryl ester transfer protein (CETP) was evaluated either in total human plasma supplemented with a tracer dose of 3H-labeled cholesteryl-ester-containing high-density lipoprotein sub-fraction 3 ([3H]CE-HDL3), or in reconstituted mixtures containing [3H]CE-HDL3, isolated low-density lipoproteins (LDL), and purified CETP. In reconstituted mixtures, all the carboxylated derivatives increased progressively and significantly the transfer of 3H-labeled cholesteryl esters from [3H]CE-HDL3 towards LDL in the 20-100 microM concentration range. Under identical experimental conditions, CETP activity was only minimally modified in the presence of all-trans-retinol. When present at a concentration of 60, 80, or 100 microM, 13-cis-retinoic acid was a significantly more potent activator of CETP activity than all the other derivatives studied (P < 0.01 in all cases). In contrast to observations made with reconstituted mixtures, only 13-cis-retinoic acid, but not palmitic acid, was able to induce a significant, concentration-dependent stimulation of CETP activity in total human plasma. In fact, differences in the ability of 13-cis-retinoic acid and palmitic acid to modulate the plasma cholesteryl ester transfer reaction were linked to their relative affinity for albumin and lipoprotein substrates: fatty-acid-poor albumin reduced CETP activity to a significantly greater extent in reconstituted mixtures containing palmitic acid than in reconstituted mixtures containing 13-cis-retinoic acid (P < 0.01 for all the incubation mixtures in the 1-10 g/l albumin concentration range); palmitic acid presented a markedly lower ability to increase the electrophoretic mobility of LDL and HDL fractions in total plasma than 13-cis-retinoic acid. In support of a key role of the negatively charged carboxylic group of 13-cis-retinoic acid in upregulating CETP activity, cholesteryl ester transfer rates correlated positively with the electrophoretic mobility of LDL (r = 0.98; P < 0.0002) and HDL (r = 0.96; P < 0.0008) in total plasma supplemented with the carboxylated compound. It is concluded that 13-cis-retinoic acid can upregulate the CETP-mediated cholesteryl ester transfer reaction both in reconstituted mixtures containing isolated lipoproteins and purified CETP, and in total normolipidemic human plasma.
Clinical laboratories must produce accurate results for patients with a minimum turn-around time. Automated commercial capillary electrophoresis instrumentation has been available to the clinical laboratory for the past five years. Our laboratory has utilised capillary electrophoresis (CE) to automate serum protein electrophoresis. We have used the technique of CE to produce clinical results for nearly two years. CE methods are also available for the quantitation of haemoglobin variants, by both isoelectric focusing and free solution techniques. Micellar electrokinetic separations by CE have been developed for some specialised drug assays and for B-group vitamin analysis, while gel-filled capillaries have the capability to separate DNA fragments, such as PCR products. Isoenzyme analysis has shown possibilities by CE, but quantitative results are needed to be clinically useful. Analysis of amino acids for newborn screening programs and as an arterial clotting indicator are being developed. The next five years should see a proliferation of clinical laboratory methods using automated CE.
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