THE RENAL EXCRETION OF Ca$sup 45$ AND Sr$sup 85$. STUDIES OF THE CLEARANCES AND DISTAL TUBULAR REABSORPTION OF THE RADIOISOTOPES (in Italian)
The mechanism of renal discrimination between calcium and strontium was investigated in dogs using stop-flow analysis and renal clearance following the intravenous injection of Ca/sup 45/ and Sr/sup 85/ administered simultaneously. Renal clearance of both radioisotopes was studied at normal urinary flow rate and during the progressive increase of urinary output, established by means of a hypertonic mannitol solution. Using stop-flow analysis, strontium, like calcium, was found to be actively reabsorbed by the distal tubule but did not appear actively lowered in concentration in proximally derived samples. Preferential urinary excretion and higher renal clearance of Sr/sup 85/ than of Ca/sup 45/ were noted at normal urinary flow rate; the ratio Sr/sup 85//Ca/sup 45/ clearance ranged from 5 to 6. As the rate of urinary flow increased the Sr/sup 85/ clearance and Ca/sup 45/ clearance increased together, but not in the same proportion. The ratio of Sr/sup 85// Ca/sup 45/ clearance decreased. This finding indicated that as tubular reabsorption of the two ions becomes less efficient, the renal discrimination between strontium and calcium decreases. At urinary flow higher than 5 to 6 ml per min the increase in strontium clearance showed a linear relation with that in calcium clearance, with the ratio of Sr/Ca clearance remaining more or less constant. Acceptrng the assumption that the distal tubule only slightly modifies the urine during mannitol diuresis, it would appear that the renal discrimination between strontium and calcium takes place mainly in the distal portion of the nephron. (auth)
- Research Organization:
- Universita, Rome
- NSA Number:
- NSA-18-008092
- OSTI ID:
- 4103472
- Journal Information:
- Minerva Nucleare (Italy) Ceased publication with Vol. 9, no. 6, 1965 Divided into G. Fis. Sanit. Prot. Radiaz. and J. Nucl. Biol. Med., Journal Name: Minerva Nucleare (Italy) Ceased publication with Vol. 9, no. 6, 1965 Divided into G. Fis. Sanit. Prot. Radiaz. and J. Nucl. Biol. Med. Vol. Vol: 7; ISSN MINUA
- Country of Publication:
- Country unknown/Code not available
- Language:
- Italian
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