Intracellular cAMP potentiates voltage-dependent activation of L-type Ca2+ channels in rat islet β-cells |
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Authors: | Takahiro Kanno Sechiko Suga J. Wu Masao Kimura M. Wakui |
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Affiliation: | (1) Department of Physiology, Hirosaki University School of Medicine, 5 Zaifu-cho, Hirosaki 036, Japan, JP;(2) Department of Neurology, The University of New Mexico, School of Medicine, Albuquerque, NM 87131, USA, MX |
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Abstract: | Intracellular cAMP-dependent modulation of L-type Ca2+ channel activation in cultured rat islet β-cells has been investigated using the patch-clamp whole-cell current recording mode. The L-type voltage-dependent Ca2+ current (I Ca) showed a fast activation followed by a slow inactivation, and was sensitive to Ca2+ channel blockers, for example nifedipine. Application of a cAMP analogue, dibutyryl cyclic AMP (db-cAMP), increased the magnitude of the peak I Ca in a concentration-dependent manner. Values of the half-activation potentials (V 1/2), taken from activation curves for I Ca, were –16.7 ± 1.8 and –21.9 ± 3.4 mV (P < 0.05) before and after application of db-cAMP, respectively, with no change of the slope factor (k) or the reversal potential. Pretreatment with a specific protein kinase A antagonist, Rp-cAMP, prevented the potentiating effect of db-cAMP. These results indicate that in rat islet β-cells, phosphorylation of cAMP-dependent kinase potentiates the voltage-dependent activation of L-type Ca2+ channels. Received: 9 September 1997 / Received after revision: 19 November 1997 / Accepted: 21 November 1997 |
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Keywords: | Cyclic AMP Ca2+ channel Islet β -cells Patch-clamp |
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