SHAPE AND SIZE CHANGES INDUCED BY TAURINE DEPLETION IN NEONATAL CARDIOMYOCYTES

Taurine is a very important organic osmolyte in most adult cells. Beca use of this property it has been proposed that large changes in the in tracellular content of taurine can osmotically stress the cell, causin g changes in its size and shape. This hypothesis was examined by measu ring cell dimensions of taurine deficient cardiomyocytes using confoca l microscopy. Incubation of isolated neonatal rat myocytes with medium containing 5 mM beta-alanine led to a 55% decrease in intracellular t aurine content. Associated with the loss of taurine was a reduction in cell size. Two factors contributed to the change in cell size. First, there was a shift in cell shape, favoring the smaller of the two cell ular configurations commonly found in the myocyte cell culture. Second , the size of the polyhedral configuration was reduced after beta-alan ine treatment. These same two events also contributed to size reductio n in cardiomyocytes incubated with medium containing 30 mM mannitol. N onetheless, some qualitative differences exist between cells osmotical ly stressed by increasing the osmolality of the incubation medium and decreasing intracellular osmolality. The results support a role for ta urine in the regulation of osmotic balance in the neonatal cardiomyocy te.