胎生及び幼若ラットにおける気管粘膜の発育分化に関する実験的研究

形態学的およびオートラジオグラフィー法による研究

抄録

The aim of the present study was to investigate the development of the tracheal mucosa morphologically and cytodynamically using 3H-thimidine autoradiography as well as light and electron microscopy.
Using rats aged 20 fetal days, 1, 2, 3, 4, 5, 6, 8, 10, 12, 14, 18, 20, 24, 26, 28 and 30 postnatal days obtained from healthy parental Wistar rats weighing 150 to 250g, experimental animals of each age group were injected 3H-thimidine 3 mc/g and sacrificed 1 hour later. A few tiny pieces of tissue were taken from the tracheal mucosa as experimental specimens. Tracheal specimens for light microscopy were embedded in paraffin, thin-sectioned and stained with HE and PAS. Another paraffin sections were used for autoradiography. With light microscopy, morphologic, numeric and distributive change in the differentiating mucosal epithelial cells of different types were examined with 3H-thimidine autoradiography. Progressive change in label indices of the mucosal epithelial cells, fibroblasts in the lamina propria and chondroblasts of the tracheal cartilage were also investigated.
As to numeric changes, the ciliated cells were proportionally small in number (10% of all the mucosal epithelial cells) in 20th day fetus. However, they rapidly increased in number after birth with beginning of respiration, becoming to 40% on the 4th postnatal day and 60% on the 30th day. The mucous cells were found to be 30% on the 20th fetal day, and then decreased in number until 10% at the birth. They increased again to 20% after 10th day and, there after became stable at 10%. The non-ciliated cells were 30% on the 20th fetal day. The numeric proportion was relatively invariable for a while after birth and became 20% on the 20th postnatal day. The basal cells were varied within the range of 20 to 10% until 14 days after birth, but settled at 20% on the 26th day and thereafter decreased to 10%. The label index of fibroblasts of the lamina propria was 14.9% on the 20th fetal day, which rapidly decresed after birth; 9.0% on the 1st neonatal day, 6.3% on the 2nd day, 5.8% on the 6th day, 2.1% on the 12th day, 4.3% on the 14th day, and thereafter, 2.0_??_3.0% until the 30th day. The label index of chondroblasts of the tracheal cartilage showed essentially identical tendency to that of fibroblasts, indicating 11.9% on the 20th fetal day, rapidly declining to 7.9% on the 1st neonatal day, 4.7% on the 2nd day, 2.0% on the 6th day, 1.9% on the 14th day and thereafter 0.6_??_1.5% until the 30th day. Thus, it can be concluded that the label index of the fibroblasts and the chondroblasts became stable after 14th postnatal day.