Localization of Laminin and Laminin beta 1 chain on Gomeruli of Developmental Rat Kidney / 체질인류학회지

ABSTRACT

Laminin, an extracellular matrix glycoprotein composed of three polypeptide chains such as alpha , beta, and gamma is distributed in basement membranes of epithelium, muscle, and nervous tissues. Laminin functions as an extracellular cytoskeleton and regulates the differentiation and polarization of cells adjacent to the basement membrane. Along with type IV collagen and heparan sulfate proteoglycan, laminin forms a spike -like structure in the renal glomerular basement membrane (GBM). It has been previously demonstrated that the distribution and immune reaction of laminin are changed in response to the conditions of glomerulonephritis and that laminin plays a role in the reformation of GBM as well as the regeneration of renal glomerular cells. In the present study, the profile of expression and distribution of laminin/laminin beta1 chain were examined in different developmental stages and upon adriamycin administration. Kidney obtained from fetuses (16, 18, and 20 days old) and infants (1 and 7 days old) of Sprague -Dawley rats were either cryosectioned for immunohistochemical assays or ultrathin -sectioned for electron microscopy using immunogold staining methods. The results were as follows 1. Intensive expression of laminin was observed in the GBM and surrounding mesenchymal tissues obtained from 16, 18, and 20 days old fetuses and in the glomerulus from one day neonates, whereas the level of staining decreased in the glomerulus from 7 days old infants. 2. Immunogold particles were observed in the comma -shaped nephron, in particular in cisternae of rough endoplasmic reticulum, vesicles and nuclear membrane of endothelial cells and mesangial cells obtained from 18 days old fetuses. 3. The immune reactions of laminin beta1 chain were trace detected in the kidney from fetuses (16, 18, and 20 days old) and weakly in tissues surrounding blood capillary and mesangial tissues from one day old neonates. 4. After 24 hours following adriamycin treatment, the reactivity of laminin was slightly enhanced in the renal glomerulus, when compared with that of untreated controls. This enhancement persisted up to 1 week of adriamycin treatment. Laminin beta1 chain was weakly detectable, while further treatment with adriamycin for another 24 hours reduced the intensity of laminin beta1 chain. Taken together, these results suggest that laminin is localized in the GBM at the high level during early fetal stages but the expression levels decrease after birth. Moreover, administration with adriamycin may result in an increase in the immune reactivities of laminin and laminin beta1 chain by renal tissue damage followed by renal regeneration.