Nonneurogenic hypoxia sensitivity in rat adrenal slices

A change in the intracellular Ca2+ ([Ca2+](i)) level induced by hypoxia was detected in rat adrenal slices by use of fura-2/AM. After hypoxic stress, an increase in [Ca2+](i) was observed only in the adrenal medulla. This inc rease was inhibited by nifedipine, but not modified by the cholinergic rece ptor blockers. The hypoxia-induced increase in [Ca2+](i) was observed in al l postnatal developmental stages to a similar extent, whereas the nicotine and high K+ sensitivities increased along with postnatal development. A 10 nM ryanodine enhanced the hypoxia-induced [Ca2+](i) increase in adult but n ot in neonatal rat slices. These results suggest the existence of an oxygen -sensing mechanism in adult rat adrenals even after sympathetic innervation . Hypoxic responses seemed to be similar both in neonate and in adult rat a drenals and were triggered by the influx of Ca2+ via L-type voltage-sensiti ve Ca2+ channels. However, the sustained [Ca2+](i) increase caused by hypox ia might depend on postnatal development and be triggered by Ca2+-induced C a2+ release (CICR). (C) 2001 Academic Press.