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Parathyroid hormone control of free cytosolic Ca 2+ in the kidney
Author(s) -
Fujii Yoshio,
Fukase Masaaki,
Tsutsumi Masaharu,
Miyauchi Akimitsu,
Tsunenari Toru,
Fujita Takuo
Publication year - 1988
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1002/jbmr.5650030508
Subject(s) - endocrinology , parathyroid hormone , medicine , extracellular , calcium , kidney , chemistry , cytosol , fura 2 , ouabain , calcium metabolism , intracellular , sodium , biology , biochemistry , enzyme , organic chemistry
We have established a perifusion system to monitor free cytosolic calcium concentrations ([Ca 2+ ] i ) in mouse kidney slices, which presumably reflects in vivo status more accurately than renal cells in culture, by means of the fluorescent calcium indicators quin‐2 and fura‐2. An increase in the extracellular calcium concentrations from 0 (no added Ca 2+ ) to 3.0 mM resulted in an increase in [Ca 2+ ] i from 52 to 239 nM. Replacement of 118 mM of extracellular Na + with choline, or the addition of ouabain, an inhibitor of Na + , K + ‐ATPase, at 10 −6 M in the perfusate caused an increase in [Ca 2+ ] i from 161 ± 13 to 873 ± 78 nM ( n = 10) and 161 ± 13 to 395 ± 68 nM ( n = 4), respectively, suggesting the possible existence of a Na + , Ca 2+ exchange mechanism in the kidney slice. We further examined the effects of PTH on [Ca 2+ ] i mobilization in the kidney. Both human PTH‐(1–34) and hPTH‐(1‐84) increased [Ca 2+ ] i within 60 s at physiologic concentrations of 10 −11 ‐10 −9 M in a dose‐dependent manner. On the other hand, an increase in intracellular cAMP in the slice was also detected above 3 × 10 −9 M hPTH‐(1–34) [base 2.1 ± 0.4 pmol/mg, 3.2 ± 0.6 pmol/mg ( p < 0.05 versus control values) 5 minutes after the application of 3 × 10 −9 M hPTH‐(1–34) and 17.3 ± 4.3 pmol/mg ( p < 0.05 versus control values) 3 × 10 −8 M hPTH‐(1–34), mean ± SEM, n = 7, p < 0.05 versus control values]. We found that the effects of PTH on [Ca 2+ ] i in our system appear to be similar to those found in cells of isolated proximal tubular cells, suggesting the cAMP and Ca 2+ dual second‐messenger system in PTH action. Thus, this perifusion system may enable us to study intracellular Ca 2+ homeostasis in the kidney.