抄録
Using Ca2+-selective microelectrodes based on the neutral carrier, ETH-1001 with polyvinyl chloride (PVC), we have measured changes in the free Ca2+ concentration of guinea pig cochlear endolymph ([Ca]e) after transient asphyxia or intravenous administration of diuretics. Under the control conditions, the endocochlear potential (EP) was +80 mV, and the [Ca]e was in the range 1.4×10−7–2.4×10−6 M (n = 16). Transient asphyxia (1–1.5 min) produced an increase in the [Ca]e with a fall in the EP, whereas the cessation of the asphyxia led to a quick recovery of both [Ca]e and EP to their control levels. Intravenous administration of furosemide (60 mg/kg) or bumetanide (30 mg/kg) also caused an increase in the [Ca]e with a fall in the EP, followed by a gradual recovery of both [Ca]e and EP. From these results, we obtained a significant correlation between EP and p[Ca]e (= –log[Ca]e), and conclude that (1) the [Ca]e is extremely low, around 10−6 M or less, under normal conditions and (2) the [Ca]e is directly correlated with EP under physiological conditions.
