Electron microscopy of lysosomal fractions from guinea pig heart

Abstract Lysosomal fractions of guinea pig heart were prepared by density gradient centrifugation and identified by biochemical measurements of acid hydrolase activity. The particulate material in samples of each fraction was sedimented by high speed centrifugation and fixed by a novel method developed for isolated organelles. Electron microscopy of the fractions showed the presence of two types of osmiphillic organelles which have previously been identified as lysosomes. Granular organelles were found in the low-density lysosomal fraction while membranous organelles were predominant in the three higher density fractions. Treatment with digitonin destroyed these organelles in all fractions and rendered the acid hydrolases unsedimentable.