Renal discrimination between strontium and calcium in rats. Effects of renal damage caused by cadmium-metallothionein.
Renal functions were damaged at the reabsorptive site by the injection of cadmium-metallothionein (Cd-MT) and its effect on discrimination of chemically similar elements was examined for the two alkaline-earth elements, calcium (Ca) and strontium (Sr). Tubular damage was induced in female Wistar rats, 7 wk old, body wt 145.1 +/- 3.5 g (mean +/- S.D.), by an intraperitoneal injection of Cd-MT (400 micrograms Cd/kg body wt). The Cd-MT injection caused increases in urinary enzymes (lactate dehydrogenase; alkaline phosphatase), glucose, and total protein. Urinary Ca and Sr increased and urinary Sr/Ca ratio decreased rapidly after the Cd-MT injection. Both changes remained at significant levels throughout the experiment. On the other hand, renal Ca and Sr levels increased with time after 18 or 24 h and changed similarly. Although plasma levels of Ca and Sr slightly increased after 30 or 36 h post-injections, the plasma Sr/Ca level remained constant. A close exponential relationship formed between the relative clearances of Ca and Sr. There was no significant difference between the exponent of the following equation (K) for the Cd-MT-injected group and that for the control group. Sr clearance/creatinine clearance = (Ca clearance/creatinine clearance)K where K = 0.408 from experimental data for the two groups. This suggests that the discrimination mechanism between Sr and Ca during the reabsorptive step in the kidney is strictly regulated.
Sugihira
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National Institute for Environmental Studies, Ibaraki, Japan.
Suzuki
K T
KT
D000469:Alkaline Phosphatase / Q000652:urine; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005260:Female; D006029:Glycosuria / Q000652:urine; D066298:In Vitro Techniques; D007668:Kidney / Q000378:metabolism*; D007674:Kidney Diseases / Q000139:chemically induced / Q000378:metabolism*; D007770:L-Lactate Dehydrogenase / Q000652:urine; D008297:Male; D008668:Metallothionein / Q000633:toxicity*; D011507:Proteinuria / Q000139:chemically induced; D051381:Rats; D011919:Rats, Inbred Strains; D013324:Strontium / Q000378:metabolism*
C004203:cadmium-binding protein; D008668:Metallothionein; D007770:L-Lactate Dehydrogenase; D000469:Alkaline Phosphatase; D002118:Calcium; D013324:Strontium