Pyruvate tolerance tests

Defective utilization of pyruvate has, however, been shown by pyruvate tolerance tests during diabetes mellitus, the abnormality not being related to coincidental factors, such as age, sex, diet, or obesity (M30). Such defective utilization of pyruvate is also shown by abnormalities in blood pyruvate following glucose administration (A5, B34, M31). 

M30. Moorhouse, J. A., Pyruvate tolerance tests in healthy subjects and in patients with diabetes mellitus. J. Lab. Clin. Med. 64, 927 (1959). 

It has been known for many years that the block in pyruvate metabolism resulting from a deficiency of thiamine, as outlined above, results in an elevated level of pyruvate in the blood [8, 9]. A pyruvate tolerance test has, therefore, been devised in which a dose of glucose is given by mouth and the blood... 

Apart from some conflicting therapeutic cltiims there is, however, little if any, convincing evidence of an associated thiamine deficiency in this condition. Goodhart and Sinclair [28] found that the levels of cocarboxylase in the blood were normal in four out of the five patients studied by them, the fifth patient, in whom a low level was found, being also an alcohol addict. Martin [29] carried out pyruvate tolerance tests following the intravenous injection of pyruvate to a series of diabetic subjects and concluded that pyruvate metabolism was normal. Thompson, Butterfield and Kelsey-Fry [30] reported on the blood pyruvate levels in glucose-insulin tests performed on a series of diabetic patients with and without neuropathy, and found that the levels were no higher in patients with neuropathy than in the other diabetics. 

In media selective for enterobacteria a surface-active agent is the main selector, whereas in staphylococcal medium sodium and lithium chlorides are the selectors staphylococci are tolerant of salt concentrations to around 7.5%. Mannitol salt, Baird-Parker (BP) and Vogel-Johnson (VJ) media are three examples of selective staphyloccocal media. Beside salt concentration the other principles are the use of a selective carbon source, mannitol or sodium pyruvate together with a buffer plus acid-base indicator for visualizing metabolic activity and, by inference, growth. BP medium also contains egg yolk the lecithin (phospholipid) in this is hydrolysed by staphylococcal (esterase) activity so that organisms are surrounded by a cleared zone in the otherwise opaque medium. The United States Pharmacopeia (1990) includes a test for staphylococci in pharmaceutical products, whereas the British Pharmacopoeia (1993) does not. 

Exploration of Bulk Tolerance at ATP Sites. Non-covalent type inhibitors have also been used to study bulk tolerance around the ATP binding sites. In this vein Hampton and co-workers have both synthesized and tested as inhibitors a large number of adenine nucleotide analogs (Figure 2f) to probe the bulk tolerance at a number of positions on the parent compound (28-31) These compounds have been used to study systematically the isoenzyme selectivity of adenylate kinases, hexokinases, thymidine kinases and pyruvate kinases with respect to bulk tolerance at many sites on the ATP molecule. Some of the most isoenzyme specific results were obtained with pyruvate kinase isoenzymes K,L and M using ADP derivatives. Here 3 -0Me-ADP was found to inhibit pyruvate kinase preferentially with a ratio of inhibitory potency of 7.6 6.0 1.0 for the K,M and L isoenzymes, respectively. Another compound, 8-NHEt-ADP, was selective for the M isoenzyme, giving a ratio of 7.1 1.2 1.0 for the M, K and L forms, respectively. 

The development of the [ C]glucose tolerance breath tests probably presents far greater problems in terms of interpretation of results than the examples cited above where use is made of a single substrate to investigate a specific metabolic area. Thus, variation of the rate of appearance of C02 in exhaled air following a [ C] glucose load will represent the combined effects of absorption, the formation of trioses, the decarboxylation of pyruvate, oxidation within the pentose shunt or the effect of gluconeogenesis. Various workers have shown that... 

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