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Biomedical subjects

J Buerkert

Publications and source records attributed to J Buerkert.

23 records · Page 2Linked to original sources
PubMed1977

Effects of acute bilateral ureteral obstruction on deep nephron and terminal collecting duct function in the young rat.

The effects of acute bilateral ureteral obstruction (BUO) of 18-h duration on deep nephron and collecting duct function were studied by micropuncture in 11 weanling rats. After release of BUO glomerular filtration rate was reduced (178+/-15 vs. 1,343+/-119 mul/min per g kidney weight in shams), while urine flow was increased averaging 17.5+/-1.3 vs. 6.8+/-0.72 mul/min per g kidney weight in controls. There was a marked increase in the absolute and fractional excretion of Na. Single nephron glomerular filtration rate of deep nephrons was reduced in the BUO group, mean 19.4+/-3.5 vs. 77.0+/-7.7 nl/min per g kidney weight in shams. Single nephron glomerular filtration rate of superficial nephrons fell to the same extent after relief of BUO. Mean tubular fluid to plasma inulin ratio of fluid from Henle's loop was 2.46+/-0.20 after relief of BUO vs. 8.23+/-0.85 in shams. This suggested a reduction in the reabsorption of Na and water before the bend of the loop of Henle, most likely in both the proximal tubule and descending limb. Fluid osmolality was depressed due to a decline in both Na and nonelectrolyte solute content. After release of BUO the percentage of filtered water remaining in the collecting duct (CD) at the base of the papilla was greater than in controls (13.3+/-2.0 and 1.72+/-0.01%, respectively) but fell significantly by the tip of the papilla to 7.92+/-1.12 vs. 1.17+/-0.02% in controls. These results indicate that water was reabsorbed along the terminal CD after relief of ureteral obstruction. In fact, a greater fraction was reabsorbed in this segment after release of BUO (5.37+/-1.58%) than after sham operation (0.55+/-0.15%). Similar changes were seen in Na excretion. Thus alterations in deep nephron function appear to contribute to the natriuresis and diuresis which follow release of BUO while terminal CD function in this model appears intact.

Animals↗
PubMed1976

On the site of decreased fluid reabsorption after release of ureteral obstruction in the rat.

Fluid reabsorption in surface nephrons was studied by micropuncture 3 hours after release of complete left ureteral ligation (LUL) or after unilateral release of bilateral ureteral ligation (BUL). In 11 rats with LUL, glomerular filtration rate (GFR) averaged 0.23 +/- 0.04 ml. per minute in the experimental vs. 1.25 +/- 0.11 ml. per minute in the control kidney. GFR averaged 0.18 +/- 0.02 ml. per minute in BUL. Single nephron glomerular filtration rate (SNGFR) was decreased in the experimental kidney of LUL or BUL when determined at proximal or distal sites as compared to the SNGFR determined in shams or the left kidney following right ureteral ligation (RUL). Fractional water excretion was increased after release of obstruction. LUL 2.72 +/- 0.66 per cent; BUL 12.3 +/- 2.82 per cent when compared to sham-operated rats (0.48 +/- 0.07 per cent) or to the untouched kidneys of the RUL group (0.60 +/- 0.09 per cent). Despite increased water and sodium excretion after release of unilateral ureteral ligation and BUL there were marked differences in tubular fluid reabsorption between these two groups. Following release of LUL there was increased fractional water reabsorption along the accessible length of surface nephrons of the experimental kidney. At 55 per cent of proximal tubular length TF/Pin averaged 4.02 +/- 0.02 in LUL vs. 2.18 +/- 0.06 in shams. The mean TF/Pin at 90 per cent of distal tubular length was 31.0 +/- 1.37 in LUL vs. 10.6 +/- 0.08 in sham-operated rats. In contrast, water reabsorption after BUL was slightly but significantly suppressed proximally (TF/Pin 1.95 +/- 0.02) and markedly depressed distally (TF/Pin 3.35 +/- 0.29). These results suggest that the change in fluid reabsorption observed after relief of LUL is located at a site beyond the accessible length of surface nephrons, most likely in the collecting duct. However, the data could also be explained by alterations in fluid reabsorption in deep nephrons. The changes in fluid reabsorption seen following release of BUL reflect the additive effects of release of obstruction and a marked reduction in functioning nephron mass.

Animals↗
PubMed1971

A micropuncture study of collecting tubule function in rats with hereditary diabetes insipidus.

The reabsorption of water and solute by the papillary collecting duct was studied during water diuresis and vasopressin-induced antidiuresis in young rats with hereditary hypothalamic diabetes insipidus. The tip of the left renal papilla was exposed and fluid was obtained by micropuncture from loops of Henle and from collecting ducts at the papillary tip, and at an average of 1 mm proximal to the tip. In water diuresis the ratio of tubule fluid to plasma (TF/P) osmolality (osm) of loop fluid was 1.73 +/-0.058 (SE); of fluid from the proximal collecting duct, 0.63 +/-0.027; and from the tip, 0.55 +/-0.024; indicating a substantial osmotic pressure difference across the collecting duct epithelium. The fraction of filtered water reabsorbed (x 100) by the terminal collecting duct was 1.58% +/-0.32. In antidiuresis the TF/P osm of loop fluid was 2.65 +/-0.109; of fluid from the proximal collecting duct, 2.20 +/-0.093; and from the tip, 2.71 +/-0.111; indicating a marked decrease in the driving force for water reabsorption. The fraction of filtered water reabsorbed (x 100) by the terminal collecting duct was reduced to 0.58% +/-0.08, while the delivery of solute to the same segment was unchanged from that in water diuresis. The glomerular filtration rate (GFR) of the right kidney declined from 327 +/-24.4 mul/min in water diuresis to 274 +/-24.4 mul/min in antidiuresis (P < 0.005); similar results were obtained in a study comparing right and left GFRs in five additional rats. Thus, fractional reabsorption (and very likely the absolute volume) of water reabsorbed by the terminal collecting duct was less in antidiuresis than in water diuresis (mean difference, 1.01% +/-0.29, P < 0.005).

Absorption↗