Mitochondrial crowding in smooth muscle cells after arterial ligation

Abstract

Although the ultrastructural appearance of mitochondrial crowding after ischemic injury has been reported in myocardial and skeletal muscles, the mechanism for this is not clear. Thirty-five branches of the mesenteric arteries removed from eight patients during surgery were examined by electron microscopy: 22 had ligatures applied 30 minutes to 4 hours before resection, 13 had no ligatures. The number of mitochondria per smooth muscle cell was significantly increased in the arterial segments under the ligature (ligated site) and immediately distal to the ligature (distal site) compared with the nonligated segments (control site). Mitochondria in ischemic cells were also noted to be swollen compared with those in nonischemic cells. Within the ligated site, paradoxically, the severity of ischemic injury correlated inversely with the increase in mitochondrial counts. In conclusion, mitochondria crowding after ischemic injury is due to both swelling and an increase in the number of organelles, and appears as early as 30 min after injury. The results also suggest that, in severely ischemic sites, cells capable of rapidly increasing their mitochondrial count may suffer less ischemic injury.