Secretory features of chondrocytes related to morphogenesis of the elastic elements in the auricular cartilage.

The well-developed secreting vacuolar system is a characteristic feature of all chondrocytes (CH) during prenatal and early postnatal ontogenesis as well as of the CH near the perichondrium in the adult rat's auricular cartilage. Two kinds of secretion vacuoles exist, dense vacuole (DV) and electron lucent vacuoles (LV). The DV are heterogeneous in size, matrix appearance and origin. The factors (organ necessities and chemical maturation) responsible for the DV matrix heterogeneity are discussed. The presence of dilated rough endoplasmic cisternae with local parts of their cisternal surfaces without bound ribosomes suggest the existence of a direct secretory pathway which bypasses the Golgi complex. During prenatal ontogenesis the extracellular matrix of the auricular cartilage consists of bundles of elastic microfibrils and primary elastic fibres. The elastic microfibrils are tubular structures with a wall composed of 3-5 subunits. After birth the primary elastic fibres are joined to form intercellular septae. The presence of matrix vesicles is discussed with regard to the fine differentiation of the auricular elastic system by their lysosomal activity.