LECTIN-BINDING SITES AND SILVER AFFINITY OF THE MACULA DENSA BASEMENT-MEMBRANES IN THE RABBIT KIDNEY

Fluorochrome-labelled lectins and the Jones method of silver impregnat ion preceded by different oxidation and enzymatic digestion procedures were used to study the patterns of glycosylation and silver affinity of the macula densa (MD) and thick ascending limb (TAL) basement membr anes of the rabbit kidney. The goal of this study was to analyse the m orphological basis of MD basement membrane permeability and its possib le role in modulation of the signal involved in tubuloglomerular feedb ack control of the juxtaglomerular apparatus. The lectin-binding patte rn and silver affinity of basement membrane differed clearly from thos e of the TAL basement membrane. The former had greater WGA and Con A a ffinity than the latter. Furthermore, the MD basement membrane lost ar gyrophilia in permanganate oxidized sections whereas that of the TAL d id not. The cell coat of MD cells differed from that of the TAL cells in that it had N-acetyl neuraminic acid and Con A binding sites. Our r esults suggest that the MD basement membrane has a distinctive macromo lecular composition which may be related to its permeability to high m olecular weight molecules.