Date of Award
Dissertation - Restricted
Doctor of Philosophy (PhD)
Howard M. Klitgaard
A membrane bound ATPase has been implicated in the active transport of sodium. This implication is based on the finding that the enzyme and sodium transport have several common characteristics. Predominant among these are the synergistic activation by Na+ and K+ in the presence of Mg++ and inhibition by certain cardiac glycosides such as ouabain. A correlation between activity of the Na+-K+ ATPase and renal reabsorption of Na+ has been found. Aldosterone, a potent salt-retaining steroid, has been shown to increase the enzyme activity in Some animals and concomitantly effect an increase in renal sodium reabsorption. Unilateral nephrectomy has been shown to have a similar effect on the remaining kidney. While these reports offer a possible biochemical mechanism for the effects of aldosterone and unilateral nephrectomy, little is known about the actual cellular location of the kidney to alterations in the demand for Na+ retention. This dissertation addresses itself to the question of the cellular localization of compensatory changes to altered levels of renal function using a coordinated biochemical and histochemical analysis.
The effects of unilateral nephrectomy, NaCl loading and aldosterone administration on Na+-K+ ATPase in the guinea pig renal cortex and medulla were studied. One week after unilateral nephrectomy, the enzyme activity of both the cortex and medulla had doubled; no change in enzyme activity was observed in the aldosterone and NaCl treated groups under the conditions employed. Histochemical reaction product was localized to the convoluted portions of the proximal and distal tubules and the thick segment of the loop Henle. Reaction product was not observed on the glomerulus and the thin segment of the loop of Henle. Unilateral nephrectomy did not alter the distribution of the enzyme.