Immunocytochemical localization of taurine in different muscle cell types of the dog and rat

The presence and distribution of the amino acid taurine in different muscle cell types of the dog and rat was examined by immunocytochemical methods. The light microscope study revealed that smooth muscle cells were similarly immunoreactive for taurine, whereas skeletal muscle fibres showed wide dif ferences in taurine immunoreactivity among individual cells. Some skeletal fibres were strongly immunoreactive whereas others did not display immunola belling. Mononucleated satellite cells, found adjacent to skeletal fibres i n a quiescent stage, were also immunostained. Other myoid cells, such as te sticular peritubular cells showed a cytoplasmic and a nuclear pool of tauri ne. By means of electron microscope immunolabelling, the subcellular locali zation of taurine was studied in vascular and visceral smooth muscle cells. Taurine was present in most subcellular compartments and frequently appear ed randomly distributed. Taurine was localized on myofilaments, dense bodie s, mitochondria, the plasma membrane and the cell nucleus. Moreover, the la belling density within individual smooth muscle cells was variable and depe nded on the state of contraction of each single fibre. Contracted cells sho wed a higher density of gold particles than relaxed cells. Unmyelinated ner ve fibres, found adjacent to smooth muscle cells from the muscularis mucosa e and the lamina propria of the stomach, were unstained or poorly stained.