AGE CHANGES IN VASCULARIZATION OF THE ADIPOSE TISSUE IN RATS

(1) The vascular bed in subcutaneous and epididymal adipose tissues of groups of rats 1 1/2, 6 and 18 months old was studied quantitatively at a magnification 200 x. 2(a) The number of capillaries per visual field which cross the focal plane decreased significantly in subcutaneous adipose tissue between 14 and 6 months and between 6 and 18 months of age. Similarly in epididymal adipose tissue there was a significant decrease in capillary number between 6 and 18 months of age. The decrease in the number of blood capillaries is probably one of the causes of the lowered release in nonesterified fatty acids from adipose tissue after norepinephrine stimulation in the older age groups. (b) The number of fat cells per visual field in subcutaneous adipose tissue decreased significantly during the period 6 to 18 months. In epididymal adipose tissue there was no significant change in the number of cells. (c) The planar area of the capillary mesh in subcutaneous and epididymal adipose tissue showed a significant increase during the period 6 to 18 months. (d) The planar area of fat cell in subcutaneous adipose tissue showed no significant change in all three groups. In epididymal adipose tissue a significant increase in area between 6 and 18 months was observed. (e) The vascularization of adipose tissue depends upon the relation between cell number and number of capillaries. The ratio cell number to number of capillaries in subcutaneous adipose tissue increase significantly with increasing age, particularly between 1 1/2 and 6 months. In epididymal adipose tissue increase this ratio with increasing age but has its maximum between 6 and 18 months.