UBC Theses and Dissertations
Histochemical localisation of adenosine triphosphatase activity in adult and newborn rat kidneys at the electron microscopial level. Lim, Wan Cheng
The histochemical localisation of ATPase enzymatic activity at the level of the electron microscope was carried out on adult and newborn kidney tissue pre-fixed in 5% glutaraldehyde buffered with 0.1 M sodium cacodylate. Both the lead method at pH 7.2 and the calcium method at pH 9.4 were used. The effects of the modifiers PHMB and L-cysteine were also studied. In the adult rat kidney, the observations of other investigators on kidney ATPase activity were substantiated. Reaction precipitate was localised at the brush border of the proximal tubules, the membranes of the basal and lateral interdigitations of the proximal and distal tubules, and the plasma membranes of the podocytic foot processes. PHMB exerted an inhibitory effect on distal tubular activity at both pH 7.2 and pH 9.4, while cysteine was inhibitory only at pH 9.4. Glomerular ATPase activity was inhibited by PHMB and L-cysteine at pH 9.4. In the newborn rat kidney, ATPase enzymatic activity was observed in the tubular elements as well as in the glomeruli. In the undifferentiated tubules, reaction product was abundant on the lateral membranes between individual cells. The luminal and basal plasma membranes, which were simple in contour, showed little or no accumulation of precipitate. However, as the microvilli became long and slender in the early stages of the differentiation of the brush border, there was a concomitant increase in the intensity of the ATPase enzymatic reaction. Similarly, reaction product became associated with the developing basal interdigitations. In the immature glomerulus, reaction precipitate was most often observed where two sets of membranes were in apposition. With differentiation, enzymatic activity was localised primarily on the podocytic foot processes. The localisation of ATPase activity at pH 9.4 was found to be influenced by the time of pre-fixation in glutaraldehyde while ATPase activity at pH 7.2 was not affected. At pH 7.2, neither tubular nor glomerular ATPase enzymatic activity responded to PHMB or L-cysteine. For both adult and newborn kidneys, the correlation between structure and function was briefly considered. The adult kidney is an important and efficient homeostatic organ. In urine formation various substances are transported across the cell membranes of the glomeruli and tubules. Ultrastructurally, the glomeruli and tubules show modifications characteristic of cells engaged in active transport processes. There is a large increase in plasma membrane surface area, as exemplified by the intricate inter-digitations of the podocytic foot processes, the elaborate basal and lateral infoldings, and the brush border of the proximal tubules. Much ATPase activity was found associated-with these plasma membranes. The newborn kidney is not as efficient as the adult kidney in maintaining body homeostasis. It is not only functionally but also morphologically immature. Most of the tubules and glomeruli are undifferentiated and do not show specialisations of the plasma membranes as seen in the adult kidney. There is also a relatively smaller amount of ATPase present in the newborn kidney. For both adult and newborn kidneys, it was postulated that at least two types of ATPases with different pH optima are present on the plasma membranes of the tubules and glomeruli.
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