An Ultrastructural Study of Mitochondria of Mammary Secretory Cells in Rabbits During Lactation and Regression Stages

Abstract

The aim of this study was ultrastructural study of mitochondria in epithelial secretory cells in mammary glands of rabbits during lactation and regression stages. Our results using conventional transmission electron microscopy has shown that the mitochondria are relatively changed during the various mammary gland development stages.We found that the average relative volume of mitochondria achieves 12.530±3.127% of cytoplasm volume in the stage of lactation. During regression mitochondrial relative volume decreased to 3.583±1.626% of the cytoplasm. This difference compared to lactation is statistically significant (p<0.05). Relative surface of mitochondria during lactation reaches 2.092±0.550 μm2/μm3 of cytoplasm. We found a decrease of relative surface of mitochondria to 0.556±0.184 μm2/μm3 of cytoplasm during regression stage. After the end of lactation, we found that the average size of mitochondria is 0.376±0.074 µm. Differences in the average size during lactation and regression are statistically significant, suggesting that mitochondria retain their size, regardless of the physiological state of activity of the mammary gland. Abundance of mitochondria during lactation is 49.34±15.2 mitochondria per 100 μm3 of cytoplasm. Abundance of mitochondria positively correlated with abundance of all cytoplasmic structures except the abundance of fat droplets, where we found a very strong negative correlation. We found 10.70±7.0 mitochondria per 100 μm3 of cytoplasm after the end of lactation. Average volume of individual mitochondria reaches 0.196±0.008 μm3. Average volume of individual mitochondria reaches 0.239±0.142 μm3 during regression. Although there is a certain tendency to increase in volume, which is also linked with an average size of mitochondria, the difference compared with the period of lactation is not statistically significant.

Keywords

• electron microscopy
• mammary glands
• mitochondria
• secretory epithelial cells