Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.4.1.18 (branching enzyme)
 628 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

MTT is widely used in biology as a probe for cell viability by virtue of its ability to generate deposits of insoluble formazan at sites of intense oxidoreductase activity. This response is generally held to reflect mitochondrial redox activity; however, extra-mitochondrial MTT reduction has also been recorded in certain cell types. Given this background, we set out to determine the major sites of formazan deposition in mammalian spermatozoa. In the mouse, most MTT reduction took place within the extensive mitochondrial gyres, with a single minor site of formazan deposition on the sperm head. By contrast, human spermatozoa generally displayed small disorganized midpieces exhibiting moderate MTT reduction activity accompanied by a major extra-mitochondrial formazan deposit on various locations in the sperm head from the neck to the anterior acrosome. Equine spermatozoa presented a combination of these two patterns, with major formazan deposition in the mitochondria accompanied by an extra-mitochondrial formazan deposit in around 20% of cells. The functionality of human spermatozoa was positively associated with the presence of an extra-mitochondrial formazan granule. Subsequent studies indicated that this extra-mitochondrial activity was suppressed by the presence of diphenylene iodonium, zinc, 2-deoxyglucose, co-enzyme Q, an SOD mimetic and NADPH oxidase inhibitors. We conclude that the pattern of MTT reduction to formazan by spermatozoa is species specific and conveys significant information about the relative importance of mitochondrial vs extra-mitochondrial redox activity that, in turn, defines the functional qualities of these cells.
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PMID:Patterns of MTT reduction in mammalian spermatozoa. 3256 57