Ultrastructural changes in the atrioventricular valves of streptozotocin-induced diabetic rats.

The present study describes ultrastructural changes in the atrioventricular (AV) valves of diabetic rats at 3, 6, 9 and 12 months. At 3 and 6 months of diabetes, the interstitial cells were characterized by an accumulation of vacuoles, lysosomes, electron-dense vesicles, mitochondria and cisternae of rough endoplasmic reticulum in the cytoplasm. There were numerous collagen fibres in the interstitial space. Unmyelinated axons were ensheathed by Schwann cells. Infiltration of macrophages was observed near the interstitial cells. Each macrophage showed a large round or oval nucleus containing heterochromatin masses at the periphery of the cell nucleus. At 9 and 12 months of diabetes, the interstitial cells contained numerous vacuoles, dilated mitochondria, agranular vesicles and a prominent multivesicular body in the cytoplasm. Degenerating unmyelinated nerve fibres were encountered near the interstitial cells. Phagocytic macrophages contained numerous vacuoles of various sizes, which occupied most of the cytoplasmic area. Several vacuoles and degenerated electron-dense granules (some of them appeared to be fragmented) were present in the cytoplasm of interstitial cells and macrophages. It is concluded that interstitial cells in the AV valves contribute to valvular dysfunction in the streptozotocin-induced diabetic rats.