One year after beginning of the experiment six streptozotocin-injected Wistar rats and six controls were anesthetized and fixed by whole-body perfusion. The diaphragms were isolated and processed for light and electron microscopy. Both the intramuscular branches of the phrenic nerve and the muscle fibers were studied morphologically and morphometrically. Moreover, two diabetic and two control rats were killed by decapitation, the diaphragms were deep-frozen and studied histochemically for myofibrillar ATP-ase.
A significant reduction of fiber cross section surface, due to reduction of both myelin and axon surfaces, was found in the phrenic nerves of diabetics. Lesions of Schwann and mesenchymal endoneural cells were the main ultrastructural changes.
The diaphragm was much thinner in diabetics than in controls. In diabetics the number of lipid droplets found in red muscle fibers was increased and the white muscle fibers were hypotrophic. These findings were confirmed by the morphometric study. Ultrastructurally, various types of lipid droplets, streaming of Z line, organelle degeneration, invagination of nuclear membrane, and increase in number of satellite cells were found in red fibers of diabetic animals. Disorientation of the triads was the most frequent lesion in white fibers of diabetics.
These results demonstrate that both neuropathy and myopathy are present in functionally related nerve and muscle from rats after 12 months of streptozotocin-induced diabetes. Both the dysmetabolic condition and the nervous lesions may have contributed to the muscular changes.
Phrenic nerve Diaphragm muscle Rat Streptozotocin diabetes Morphology