title: Age-related alterations in calbindin-D28K induction by 1,25-dihydroxyvitamin D3 in primary cultures of rat renal tubule cells.
abstract: In vivo studies have indicated that renal calbindin-D28K protein and mRNA levels decrease in adult and old rats, and this decrease parallels the age-associated decline in serum 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] levels. However, diminished renal responsiveness to 1,25-(OH)2D3 with advancing age could also contribute to decreased calbindin-D28K expression. To study renal responsiveness with age, primary cell cultures were established from the kidney cortices of young (1 month old), adult (10-12 months old), and old (20-24 months old) rats. Cells were incubated in medium K-1 containing 2% fetal calf serum. Calbindin-D28K protein levels were determined by Western blot and enzyme-linked immunosorbent assay. In young animals, the levels of calbindin-D28K declined from 12.1 +/- 1.3 micrograms/mg protein in the intact kidney to 1.6 +/- 0.07 micrograms/mg protein in cells that had been cultured for 3 days in the absence of 1,25-(OH)2D3. This sharp decline in calbindin-D28K protein concentration moderated by days 6-8. The continuous presence of 10(-7) M 1,25-(OH)2D3 in the medium did not abolish the decline. The low levels of calbindin-D28K in the cells cultured in the absence of 1,25-(OH)2D3 provided an excellent experimental system in which to compare the response of the cells to 1,25-(OH)2D3 between age groups. In cultured cells treated with 1,25-(OH)2D3 for 72 h, calbindin-D28K induction was greater in cells from adult and old animals compared to cells from young animals. The ratios of calbindin-D28K content (with vitamin D/without vitamin D) were 2.2 +/- 0.2, 4.7 +/- 0.5, and 7.1 +/- 1.5 for young, adult, and old cells, respectively. These studies suggested that the observed in vivo decrease in renal calbindin-D28K with age is primarily due to the lowered circulating 1,25-(OH)2D3.
authors.affiliation: Geriatric Research, Education, and Clinical Center, Veterans Affairs Medical Center, St. Louis, Missouri 63125.
authors.forename: M L
authors.initials: ML
authors.lastname: Chen
authors.forename: M
authors.initials: M
authors.lastname: Boltz
authors.forename: S
authors.initials: S
authors.lastname: Christakos
authors.forename: H J
authors.initials: HJ
authors.lastname: Armbrecht
mesh_terms: D000375:Aging; D000818:Animals; D015153:Blotting, Western; D064092:Calbindin 1; D064026:Calbindins; D002117:Calcitriol / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D007672:Kidney Cortex / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D007684:Kidney Tubules / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344; D064030:S100 Calcium Binding Protein G / Q000096:biosynthesis* / Q000302:isolation & purification; D013997:Time Factors
chemical_list: C576500:Calb1 protein, rat; D064092:Calbindin 1; D064026:Calbindins; D064030:S100 Calcium Binding Protein G; D002117:Calcitriol