TY - JOUR
T1 - Stimulation of calcium uptake by parathyroid hormone in renal brush-border membrane vesicles. Relationship to membrane phosphorylation
AU - Khalifa, S.
AU - Mills, S.
AU - Hruska, K. A.
PY - 1983
Y1 - 1983
N2 - The effect of parathyroid hormone (PTH) on Ca2+ uptake was studied in brush-border membrane vesicles (BBMV) prepared from the kidneys of dogs administered 4-5 μg/kg of bovine PTH 1-84 in vivo. PTH stimulated Ca2+ uptake at 20 s of incubation from control values of 231 ± 21 to 306 ± 30 pmol/mg of protein, p<0.001. The stimulation of Ca2+ uptake by PTH was not reversed by incubation of the BBMV with the Ca2+ ionophore, despite the fact that Ca2+ uptake was several times greater than the expected uptake at equilibrium, indicating that most of the uptake represented Ca2+ binding to the BBMV. In BBMV from kidneys exposed to PTH, hypotonic lysis or increasing the osmolality of the solution external to the BBMV did not affect Ca2+ uptake. These data also indicated that the largest fraction of Ca2+ uptake in the presence of a chemical potential represented binding of Ca2+ to BBMV. Ca2+ binding was initially to the exterior of the BBMV, then translocated within the membrane and to the interior vesicular face as assessed by chelation of Ca2+ bound to the BBMV by ethylene glycol bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid. Incubation of BBMV from kidneys exposed to PTH with gentamicin, which competes with Ca2+ for anionic phospholipid-binding sites, reversed the stimulatory effects of PTH on Ca2+ uptake. Phosphorylation of BBMV and PTH treatment in vivo had similar effects on BBMV phospholipid composition increasing the levels of anionic phospholipids. Phosphorylation of the BBMV also produced gentamicin-inhibitable increases in membrane Ca2+ binding. Phosphorylation of the BBMV from kidneys exposed to PTH was inhibited suggesting a higher state of phosphorylation in vivo. The data demonstrate that PTH administered in vivo stimulated Ca2+ binding in BBMV that was gentamicin inhibitable and associated with an increase in the membrane content of anionic phospholipids.
AB - The effect of parathyroid hormone (PTH) on Ca2+ uptake was studied in brush-border membrane vesicles (BBMV) prepared from the kidneys of dogs administered 4-5 μg/kg of bovine PTH 1-84 in vivo. PTH stimulated Ca2+ uptake at 20 s of incubation from control values of 231 ± 21 to 306 ± 30 pmol/mg of protein, p<0.001. The stimulation of Ca2+ uptake by PTH was not reversed by incubation of the BBMV with the Ca2+ ionophore, despite the fact that Ca2+ uptake was several times greater than the expected uptake at equilibrium, indicating that most of the uptake represented Ca2+ binding to the BBMV. In BBMV from kidneys exposed to PTH, hypotonic lysis or increasing the osmolality of the solution external to the BBMV did not affect Ca2+ uptake. These data also indicated that the largest fraction of Ca2+ uptake in the presence of a chemical potential represented binding of Ca2+ to BBMV. Ca2+ binding was initially to the exterior of the BBMV, then translocated within the membrane and to the interior vesicular face as assessed by chelation of Ca2+ bound to the BBMV by ethylene glycol bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid. Incubation of BBMV from kidneys exposed to PTH with gentamicin, which competes with Ca2+ for anionic phospholipid-binding sites, reversed the stimulatory effects of PTH on Ca2+ uptake. Phosphorylation of BBMV and PTH treatment in vivo had similar effects on BBMV phospholipid composition increasing the levels of anionic phospholipids. Phosphorylation of the BBMV also produced gentamicin-inhibitable increases in membrane Ca2+ binding. Phosphorylation of the BBMV from kidneys exposed to PTH was inhibited suggesting a higher state of phosphorylation in vivo. The data demonstrate that PTH administered in vivo stimulated Ca2+ binding in BBMV that was gentamicin inhibitable and associated with an increase in the membrane content of anionic phospholipids.
UR - http://www.scopus.com/inward/record.url?scp=0021032934&partnerID=8YFLogxK
M3 - Article
C2 - 6643490
AN - SCOPUS:0021032934
SN - 0021-9258
VL - 258
SP - 14400
EP - 14406
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 23
ER -