Biochemical characterization of subcellular particles in fetal and neonatal rats

By a variety of methods, such as ultracentrifugation in different media, hypoosmotic activation and hydrostatic compression, subcellular particles were characterized at different perinatal ages and compared to the adult rats. Fetal mitochondria elicited a higher density, an increased osmotic space and a greater resistance to compression. The size of these particles was larger than in the adults. Mitochondria in the 1-day-old animals were freely permeable to sucrose and their external membrane was more resistant to hypoosmotic activation. Lysosomes were shown to decrease their sucrose permeability and their resistance to hypoosmotic activation with development. Moreover, the size of the lysosomes increased with development.