A cytochemical study of gl.ycocalyx and the membrane cholesterol of rat glomerular podocytes.

Abstract

In order to elucidate the cytochemical properties of rat podocyte's membranes, the authors studied the constituents and distribution of glycocalyx and membrane cholesterol. Chromic-phosphotungstic acid (Cr-PTA) stain combined with enzyme digestive tests was used for the glycocalyx analysis. A digitonin fixation method was applied for the detection of membrane cholesterol. On the whole surface of podocytes, glycocalyx showed a strongly positive reaction to Cr-PTA. In normal rats, the reactivity on the urinary surface above the slit membrane of the podocyte foot processes was decreased after treatments with neuraminidase, hyaluronidase and heparitinase. The reactivity on the basal surface below the slit membrane disappeared only after treatment with chondroitinase ABC. In Puromycin Aminonucleoside nephrosis (PAN) rats, the foot processes were effaced extensively. Though a highly positive reactivity of Cr-PTA was observed on the urinary surface of the podocytes, the basal surface reacted weakly. The positive reaction of the urinary surface was not affected by the treatments with neuraminidase, hyaluronidase and heparitinase, but the weak reaction of the basal surface disappeared completely through chondroitinase ABC treatment. The distribution of membrane cholesterol was clearly revealed by the digitonin fixation method, showing digitonin cholesterol complexes of localized trilamellar structures. In normal rat podocytes the complexes were found on the urinary surface, with only a few on the basal surface. In PAN rats the complexes were seldom noticed either on the urinary or basal surfaces. The heterogeneous distribution of glycocalyx and membrane cholesterol seen in normal rat podocytes are changed remarkably under nephrotic condition.