RESUMEN
Stereological methods were applied in the qantitative ultrastructural analysis of the chromaffin cells in adrenal medulla of normal adult guinea pigs.The main result includes:(1)The average volume(V)of each cell(714?m~3)and its nucleus (167?m~3);(2)volume density(Vv)of mitochondria(0.082?m~3/?m~3),lysosomes (0.0045?m~3/?m~3),rough-endoplasmic reticulium(0.013?m~3/?m~3),smooth-endopas- mic reticulium including Golgi apparatus(0.024?m~3/?m~3)and granule vesicles (0.23?m~3/?m~3);(3)surface density(Sv)of cell membrane(0.87/?m~2/?m~3)and mitochondrial outer membrane(0.90?m~2/?m~3);(4)numerical density(Nv)of mitochondria(0.89/?m~3),lysosomes(0.11/?m~3)and granule vesicles(59.98/?m~3); (5)the mean diameter of granule vesicles(144 nm),In addition,several small- granule chromaffin cells were quantified separately from the general chromaffin cells.They contain granule vesicles with an average diameter of 97 nm and show a significant difference in surface density of cell membrane(1.54?m~2/?m~3)from that relevant value of general chromaffin cells(P