Hormone-regulated Ca²⁺ channel in rat hepatocytes revealed by whole cell patch clamp

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• 作者：J. Duszynski ; M. Elensky ; J. Y. Cheung ; D. L. Tillotson ; K. F. LaNoue
• 关键词：DOC ; deoxycholate ; DMSO ; dimethylsulfoxide ; EDTA ; ethylene-diaminetetraacetic acid ; SERCA 1 ; sarcoplasmic/endoplasmic reticulum Ca²⁺-ATPase type 1 ; SDS-PAGE ; sodium dodecyl sulphate polyacrylamide gel electrophoresis ; SR ; sarcoplasmic reticulum
• 刊名：Cell Calcium
• 出版年：1995
• 出版时间：July 1995
• 年：1995
• 卷：18
• 期：1
• 页码：19-29
• 全文大小：930 K

文摘

An inward current responsible for hormone regulated Ca²⁺ entry has been identified in cultured rat hepatocytes using whole cell patch clamp. Addition of 20 nM vasopressin or of 100 μM ATP induced the inward current, which could be observed more clearly after blocking an outward K⁺ current. This large outward K⁺ current, which appeared after addition of vasopressin or ATP, could be blocked either by replacing K⁺ with Cs⁺ in the external medium and in the pipette solution, or by simply including 0.5 μM apamin in the K⁺-containing external medium. The outward current appears to be carried by a Ca²⁺ activated K+ channel.

In the presence of apamin, hepatocytes pretreated with vasopressin in a Ca²⁺-free media reveal an inward current on addition of external Ca²⁺ (5 mM). The current could also be elicited by addition of vasopressin when cells are preincubated in the presence of 5 mM external Ca²⁺. No current is seen on addition of Ca²⁺ in the absence of vasopressin. Initially, the inward current was ca 200–300 pA at −60 mV, but it declined rapidly over 3 min to ca 20 pA. The current approached zero, as an asymptote at positive potential, and appeared to be somewhat inwardly rectifying. Additions of 5 mM Mn²⁺ or 5 mM Ba²⁺ in place of Ca²⁺ produced little or no current. An inhibitor of ER Ca²⁺-ATPase, thapsigargin, could also trigger the cascade of events leading to plasma membrane conductance of Ca²⁺. The data suggest that hormone-stimulated Ca²⁺ entry into hepatocytes is mediated by a Ca²⁺-release activated channel highly specific for Ca²⁺. This is the first demonstration of such a channel in hepatocytes, though similar ones have been described in mast cells, in vascular endothelial cells and T-lymphocytes.