Noninvasive 64Cu-ATSM and PET/CT assessment of hypoxia in rat skeletal muscles and tendons during muscle contractions.

Abstract

UNLABELLED:

The purpose of the present study was to investigate exercise-related changes in oxygenation in rat skeletal muscles and tendons noninvasively with PET/CT and the hypoxia-selective tracer (64)Cu-diacetyl bis(N(4)-methylthiosemicarbazone) (ATSM) and to quantitatively study concomitant changes in gene expression of 2 hypoxia-related genes, hypoxia-inducible factor 1alpha (HIF1alpha) and carbonic anhydrase III (CAIII).

METHODS:

Two groups of Wistar rats performed 1-leg contractions of the calf muscle by electrostimulation of the sciatic nerve. After 10 min of muscle contractions, (64)Cu-ATSM was injected and contractions were continued for 20 min. PET/CT of both hind limbs was performed immediately and 1 h after the contractions. The exercise group (n = 8) performed only muscle contractions as described, whereas the other group, exercise plus cuff (n = 8), in addition underwent cuff-induced hypoxia during the first PET/CT scan. Standardized uptake values (SUVs) were calculated for the Achilles tendons and triceps surae muscles and were correlated to gene expression of HIF1alpha and CAIII using real-time polymerase chain reaction.

RESULTS:

Immediately after the contractions, uptake of (64)Cu-ATSM was significantly increased, by approximately 1.5-fold in muscles and 1.3-fold in tendons, compared with resting conditions. The significant increase was maintained in late PET scans in stimulated muscles and tendons independently of cuff application. In muscles, SUV correlated significantly with gene expression of HIF1alpha and CAIII, whereas this coherence was not found in tendons.

CONCLUSION:

We found enhanced uptake of (64)Cu-ATSM in both early and late PET scans, thereby supporting the possibility that (64)Cu-ATSM registers exercise-induced transient hypoxia in both skeletal muscles and force-transmitting tendons. The fact that skeletal muscles but not tendons showed upregulation of HIF1alpha and CAIII could indicate that healthy tendons are less responsive than skeletal muscles to low levels of oxygen.

• Authors: Dorthe Skovgaard, Michael Kjaer, Jacob Madsen, Andreas Kjaer
• Journal: Journal of nuclear medicine : official publication, Society of Nuclear Medicine (J Nucl Med) Vol. 50 Issue 6 Pg. 950-8 (Jun 2009) ISSN: 0161-5505 [Print] United States
• PMID: 19443591 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Coordination Complexes
• Copper Radioisotopes
• Hif1a protein, rat
• Hypoxia-Inducible Factor 1, alpha Subunit
• Organometallic Compounds
• RNA, Messenger
• Thiosemicarbazones
• copper (II) diacetyl-di(N(4)-methylthiosemicarbazone)
• Carbonic Anhydrase III

Topics

• Animals
• Carbonic Anhydrase III (genetics)
• Cell Hypoxia
• Coordination Complexes
• Copper Radioisotopes
• Hypoxia-Inducible Factor 1, alpha Subunit (genetics)
• Male
• Muscle Contraction
• Muscle, Skeletal (metabolism)
• Organometallic Compounds
• Positron-Emission Tomography (methods)
• RNA, Messenger (analysis)
• Rats
• Rats, Wistar
• Tendons (metabolism)
• Thiosemicarbazones
• Tomography, X-Ray Computed (methods)