3H-Inulin and electrolyte concentrations in Bowman's capsule in rat kidney

Abstract

Micropuncture experiments were performed on Bowman's capsules in male and female non-diuretic Munich rats. 55 samples were collected and analysed for Na, Cl, K, Ca, P, Mg and 3H-inulin contents. Their electrolyte concentrations were compared to the corresponding concentrations obtained from plasma artificial ultrafiltrates. Compared to normal Wistar rats, our Munich rats had several special characteristics: high arterial pressure (115-155 mm Hg), high concentrating ability (phi equals 2684 mOsm/1) and high NaCl reabsorption capacity. Whole kidney GFR was low in males (0.361 ml/min/kidney/100 g B.W.). 3H-Inulin concentration was the same in plasma and glomerular ultrafiltrates (GF). The corresponding ratio (GF/P) in equals 1.03 plus or minus 0.01 (N equals 55) confirmed the lack of sieving effect for inulin. GF electrolyte concentrations were, for Na, Cl, K, Ca, P, Mg respectively 139 plus or minus 0.05, 1.46 plus or minus 0.07 and 0.52 plus or minus 0.04 ml/1 (N equals 23) in females and 141 plus or minus 2, 120 plus or minus 2, 3.84 plus or minus 0.07, 1.31 plus or minus 0.03, 1.78 plus or minus 0.05 and 0.48 plus or minus 0.01 mM/1 (N equals 32) in males. Comparison of ultrafiltration trough a cuprophan membrane and glomerular ultrafiltration led to the following conclusions: For Na, Cl and P artificial and glomerular ultrafiltration produced identical results. On the other hand, for Ca and to a lesser extent for Mg and K ions, artificial ultrafiltration did not accurately reflect the true glomerular ultrafiltrate composition. The reasons for these differences are discussed below.

A micropuncture study of renal phosphate transport in rats with chronic renal failure and secondary hyperparathyroidism.

“…This correction factor is in close agreement with that found by Strickler et al (7). Moreover, Le Grimellec et al (19) found that the phosphate concentration in fluid collected from Bowman's capsule of rats agrees closely with that found in ultrafiltrates of whole plasma through Cuprophan membranes (Enka AG., Plant Wuppertal-Bjarmen Wuppertal 2 West Germany). In the text and figures, plasma 32P04 refers to UF 32po4, i.e.…”

Relationship between Phosphaturia and Acute Hypercapnia in the Rat

“…Parathyroidectomy (32, 33) and phosphate loading (31-33) appear to have no discernible effect on the ultrafilterable fraction of phosphate as determined in in vitro systems. Moreover, LeGrimellec et al (34) have shown that the filterability of phosphate across the glomerular filtration barrier is essentially identical to the value measured across cuprophane. Thus, it appears that the maximum increment in filtered load which could be attributed to a change in phosphate ultrafilterability must be less than 10%.…”

Evidence for an Intrinsic Renal Tubular Defect in Mice with Genetic Hypophosphatemic Rickets

“…Increased fractional excretion ofphosphate in mutants (47.2 +4 vs. 30.8+2% in controls) was associated with reduced fractional and absolute reabsorption in the proximal convoluted tubule and more distal sites. Acute thyroparathyroidectomy (TPTX) increased phosphate reabsorption in both mutants and controls with a fall in fractional phosphate excretion to _7.5% in both groups indicating that PTH modified the degree of phosphaturia in the intact mutants.…”