Effect of Hypothermia on Intracellular Ca 2+ in Rabbit Renal Tubules Suspended in UW-Gluconate Preservation Solution

Author： Mcanulty J.F. Ametani M.S. Southard J.H. Belzer F.O.

ISSN： 0011-2240

Source： Cryobiology, Vol.33, Iss.1, 1996-02, pp. : 196-204

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Abstract

Altered cellular calcium (Ca) homeostasis may be important in mediating hypothermic injury in preserved kidneys. In this study the effect of hypothermic (5#°C) storage on ionized intracellular Ca concentration ([Ca] i ) in rabbit tubules was examined using Indo-1. Tubules were stored up to 250 min in UW-gluconate solution containing either 0.0, 0.5, 1.5, or 5.0 m M Ca (yielding about 3.6, 62, 371, and 1,010 mu M ionized solution Ca (Ca 2+ ) at 5#°C, respectively). [Ca] i increased to about 1,600 n M within 1 min after suspension in UW solution followed by a decrease in [Ca] i during the subsequent 60 min in all groups, suggesting mitochondrial Ca sequestration. Thereafter, [Ca] i either 1) increased in tubules incubated with 1.5 and 5.0 m M Ca to levels greater than 2,500 n M; 2) decreased to about 800 n M in tubules incubated with 0.5 m M Ca and then remained stable; or 3) continued to decrease in tubules incubated with 0.0 m M added Ca to reach an apparent steady-state concentration of about 175 n M after 180 min of incubation. The early spike in [Ca] i was unaffected by adding EGTA (solution Ca 2+ = 50 n M ). Ryanodine eliminated the [Ca] i spike, indicating that cooling in UW-gluconate solution caused release of endoplasmic reticulum Ca. This study shows that [Ca] i initially increases after exposure to UW-gluconate solution and appears to be transiently buffered through intracellular, probably mitochondrial, sequestration. Saturation of cellular buffer mechanisms resulted in a sustained dependence of [Ca] i on extracellular Ca 2+ . These results support the hypothesis that the effect of Ca on kidney viability is related to solution-induced alterations in [Ca] i .