Diurnal variation in human tear enzymes

Fullard, Roderick J. & Carney, Leo G. (1984) Diurnal variation in human tear enzymes. Experimental Eye Research, 38(1), pp. 15-26.

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A fluorometric technique for measuring the activities of lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) in human tear fluid is described. Measurement of separate LDH and MDH activities during the day resulted in fluctuating values with no definite pattern. However, a consistent diurnal pattern emerged when the tear LDH/MDH ratio was measured for individual tear sample. The tear LDH/MDH ratio was highest upon waking, declining soon after to a stable level for the remainder of the day. Evidence for a corneal epithelial origin of tear LDH and MDH is discussed, as well as the ability of the technique to detect differences in the metabolic status of the epithelium between the open-eye and closed-eye environments. Possible causes of the elevation of the tear LDH/MDH ratio following lid closure are unbinding of intracellular M-type LDH within epithelial cells and increased cell membrane permeability, both processes occurring in response to reduced cellular energy content under the more hypoxic conditions of lid closure. Although the nature of the present experiment did not allow any conclusive statement, de novo LDH synthesis may also be contributing to the increased tear LDH/MDH ratio. Deliberate corneal epithelial surface disruption was found to have no quantifiable effect on the tear LDH/MDH ratio.

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13 citations in Scopus
15 citations in Web of Science®
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ID Code: 3133
Item Type: Journal Article
Refereed: Yes
Additional Information: For more information, please refer to the journal’s website (see link) or contact the author. Author contact details: l.carney@qut.edu.au
Keywords: Circadian Rhythm, L, Lactate Dehydrogenase/, metabolism, Malate Dehydrogenase/, metabolism, Tears/, enzymology, Cornea/enzymology, Cornea/injuries, Epithelium/enzymology, Eyelids/physiology, Fluorometry, Humans
DOI: 10.1016/0014-4835(84)90134-9
ISSN: 0014-4835
Subjects: Australian and New Zealand Standard Research Classification > MEDICAL AND HEALTH SCIENCES (110000) > OPTOMETRY AND OPHTHALMOLOGY (111300)
Divisions: Current > QUT Faculties and Divisions > Faculty of Health
Copyright Owner: Copyright 1984 Elsevier
Deposited On: 31 Jan 2006 00:00
Last Modified: 15 Jan 2009 06:54

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