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Denver Genetic Laboratories
 

Mitochondrial Respiratory Chain Enzyme Assay (or Microassay)

Clinical Test Information - UCD Biochemical Genetics Laboratory


 

CPT Code:

82657 x 6 (six assays are performed).

Availability:

Monday - Friday, 0800 - 1700.

Turnaround Time:

One month (or six weeks if combined with blue native electrophoresis with in-gel mitochondrial enzyme analysis).

Specimen Requirements:

  • Muscle tissue: Please see the detailed instructions below. Minimum 60 mg required.
  • Liver tissue: Please see the detailed instructions below. Minimum 20 mg required. Samples of <60 mg will require microassay (please note that the microassay is less robust than the regular assay).

MUSCLE

Muscle biopsies must be obtained without the use of electrocautery and must be completely processed within 5 to 10 minutes of being excised. Muscle biopsies should be preferably about 120 mg in size. They must be frozen immediately in liquid nitrogen or on dry ice. They cannot be placed in any preservative including OCT. They must be stored in a microvial at -70° C until shipment to the laboratory on dry ice.

LIVER

Liver samples can be obtained as a wedge biopsy or as a needle biopsy. It is important to ensure that sufficient liver tissue is obtained.  If using a needle biopsy, obtain two (2) needle biopsies 14 Gauche Bard monopty instrument 2 cm length.  Postmortem samples have to be obtained within 6 hours of death, but preferably within 2 hours of death as interpretation will become more difficult with time.

Place the liver biopsy in either Parafilm or aluminum foil, and then place in a 2 ml cryotube, then close the screw cap tightly.

Freeze immediately in liquid nitrogen or on dry ice, and maintain in frozen condition. If possible, weigh liver biopsy before placing in the cryotube.  If the specimen was not weighed before it was frozen, DO NOT attempt to weigh a frozen sample as the samples degrade very easily.  Instead, ship the sample to the RC Core Lab without a weight.  Lab personnel will weigh the sample.

Keep sample in -70° C freezer. Samples will not be stable at -20° C. Samples that have thawed even for a short period are not acceptable.  Weighing the sample will cause thawing.  DO NOT ATTEMPT TO WEIGH A FROZEN SAMPLE.

ALL MITOCHONDRIAL ASSAY SPECIMENS

All tissue specimens should be frozen immediately in liquid nitrogen, or on dry ice, and stored at -70° C. Specimens should be shipped frozen on dry ice.

Please also enclose a completed requisition form for mitochondrial respiratory chain enzyme assays (please make sure that you enclose the appropriate requisition form, and that both pages of the requisition form are completed).

Primary contact for mitochondrial enzyme assay:

Marisa Friederich, PhD
Phone: 303-724-3841
Email: marisa.friederich@ucdenver.edu

Interpretive Reference Ranges:

     Muscle (in nmol/min per mg protein):
            Complex 1: 23.6 – 74.8
            Complex 2: 49.0 – 133.4
            Complex 3: 5.7 – 31.4
            Complex 2-3: 40.7 – 109.8
            Complex 4: 1.1 – 3.8
            Citrate synthase: 159.8 – 353.3
            (Ratios of complex activities over citrate synthase and over complex 2
            are provided. Subject to interpretation.)

      Liver (in nmol/min per mg protein):
            Complex 1: 14.4 – 56.0
            Complex 2: 174.7-309.8
            Complex 3: 13.8 – 27.6
            Complex 2-3: 10.8 – 107.3
            Complex 4: 0.5 – 3.2
            Citrate synthase: 59.5 – 109.3
            (Ratios of complex activities over citrate synthase and
            over complex 2 are provided. Subject to interpretation.)

Use:

Diagnosis of mitochondrial respiratory chain diseases.

Methodology:

Spectrophotometric enzyme assays.