Ultrastructural Changes of the Renal Corpuscle of the Mouse with Age

Morphological difference of the renal glomerulus at different age groups have been studies in one week-old, five weeks-old, eight weeks-old, six months-old, twelve months-old, eighteen months-old, twenty-four months-old, and thirty months-old ICR mice. Pieces of the tissue taken from the renal corticies were fixed in 2.5% glutaraldehyde-1.5% paraformaldehyde solution (0.1 Millonig's phosphate buffer pH 7.3), and 1% osmium tetroxide solution (0.1 M Millonig's phosphate buffer, pH 7.3), and were embedded in araldite mixture. The ultrathin sections were stained with uranyl acetate and lead citrate solution, and were observed under a JEM 100CX-II electron microscope. The results were as follows: 1 In the one week-old mouse, thicknesses of the three layers of the glomeluar basal lamina (lamina densa, lamina rara interna and lamina rara externa) are similar, but in the five weeks-old mouse, thick lamina densa becomes a greater portion of the thickness of whole glomerular basal lamina. 2. No difference was noticed between thickness of the renal glomerular basal lamina of the five weeks-old mouse compare with that of the one week-old one, but basal lamina of the eight weeks-old one is thickened considerably and thicknesses were maintained through twelve months-old one. After eighteen months, the thickness of the glomerular basal lamina is increased remarkably. 3. After eighteen months, electron dense deposits within the basal lamina of the renal glomeruli are observed frequently. 4. Amount of the microfilaments in the mesangial cells and the mesangial matrices are increasing during aging. 5. The thicknesses of the basal laminae of the Bowman's capsule are increasing during aging. 6. After twenty four months, the proximal tubular cell-like parietal cells with well developed microvilli are observed frequently. From the above results, it was suggested that the renal glomerulus matures structurally in five weeks, and the function of the glomerulus is suppressed after eighteen months.