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H Lubowitz

Publications and source records attributed to H Lubowitz.

28 records · Page 2Linked to original sources
PubMed1969

Ion movements in human red cells independent of the sodium pump.

1. A study was made of the dependence on external Na of the movements of Na and K in human red cells. Special attention was given to ouabain-insensitive movements. The effect of internal Na on Na influx, and the influence of some sulphydryl inhibitors on ion movements and metabolism was also investigated.2. External Na stimulated ouabain-insensitive Na efflux and K influx. There was also a ouabain-insensitive component of Na influx that was raised on increasing the internal Na concentration. Exchange diffusion of Na appears to occur in the presence of ouabain and external K.3. Net transport of Na and K in the presence of ouabain was independent of external Na, as was also lactate production.4. Ethacrynic acid partially inhibited the Na pump; the Na-dependent components of Na efflux and K influx in the presence of ouabain were completely inhibited by ethacrynic acid. Both ouabain-sensitive and ouabain-insensitive adenosinetriphosphatase activities were inhibited by ethacrynic acid indicating a non-specific effect of this compound. Iodoacetamide decreased only the ouabain-insensitive ATPase activity.5. The results suggest that when the Na pump is blocked by ouabain, part of the residual ion movements can be attributed to exchange diffusion.

Adenosine Triphosphatases↗
PubMed1969

On the influence of extracellular fluid volume expansion on bicarbonate reabsorption in the rat.

Bicarbonate reabsorption is classically regarded as a rate-limited process characterized by saturation kinetics. The tubular maximum (Tm), however, varies with glomerular filtration rate. Thus bicarbonate reabsorption, in common with sodium reabsorption, is characterized by glomerulo-tubular balance. The examination of bicarbonate reabsorption is accomplished using the bicarbonate titration technique; however, this method in its traditional form leads to marked expansion of extracellular fluid (ECF) volume. The possibility exists, therefore, that glomerulo-tubular balance for bicarbonate is altered by the volume expansion and thus that the classic pattern of reabsorption may actually reflect inhibited bicarbonate reabsorptive capacity. The present studies were performed in rats to examine this possibility. Bicarbonate titration studies were performed in two groups of animals: (a) those in which ECF volume expansion was minimized; and (b) those in which ECF volume expansion was exaggerated. In the first group, no Tm for bicarbonate was observed either in the majority of individual rats studied or in a group plot for all rats studied despite the fact that plasma bicarbonate concentrations were increased to values in excess of 60 mEq/liter. In the second group, a clear Tm was demonstrated both in individual animals and in group data and there was a lowered threshold for the excretion of bicarbonate. The data thus lend support to the view that the "normal" Tm for bicarbonate may actually represent an inhibited level of bicarbonate reabsorption induced by ECF volume expansion.

Animals↗
PubMed1967

Glucose titration studies in patients with chronic progressive renal disease.

Glucose titration studies were performed on 17 patients with either chronic pyelonephritis or chronic glomerulonephritis. Glomerular filtration rates for the group ranged from 4.3 to 58.1 ml per minute. In none of the patients in whom the glomerular filtration rate was over 15 ml per minute was there appreciable splay, and the mean titration curve for these patients resembled that obtained by Smith and associates in normal man (1). In half of this group of eight patients, GFR ranged from 16.6 to 22.7 ml per minute; in the other half values ranged from 42.3 to 58.1 ml per minute. Yet, the mean titration curves were identical for the two groups. In addition, no difference was observed in the titration curves for patients with pyelonephritis and those with glomerulonephritis. In patients with GFR values below 15 ml per minute, increased splay was observed, and below a GFR of 10 ml per minute, the splay was very marked. Both the absence of exaggerated splay in patients with reduction of glomerular filtration rate by as much as 85%, and the emergence of exaggerated splay in patients with more marked reduction of GFR, require explanation. Theoretical considerations are presented in the text.

Adolescent↗