Temperature-sensitive intracellular Mg2+ block of L-type Ca2+ channels in cardiac myocytes.

نویسندگان

  • Kaoru Yamaoka
  • Tsunetsugu Yuki
  • Kayoko Kawase
  • Makoto Munemori
  • Issei Seyama
چکیده

We examined the concentration-dependent blocking effects of intracellular Mg2+ on L-type Ca2+ channels in cardiac myocytes using the whole cell patch-clamp technique. The increase of L-type Ca2+ channel current (I(Ca)) (due to relief of Mg2+ block) occurred in two temporal phases. The rapid phase (runup) transiently appeared early (<5 min) in dialysis of the low-Mg2+ solution; the slow phase began later in dialysis (>10 min). Runup was not blocked by intracellular GTP (GTP(i)). The late phase of the I(Ca) increase (late I(Ca)) was suppressed by GTP(i) (0.4 mM) and was observed in myocytes of the guinea pig or frog at higher (32 or 24 degrees C, respectively) rather than lower temperatures (24 or 17.5 degrees C, respectively). At pMg = 6.0, raising the temperature from 24 to 32 degrees C evoked late I(Ca) with a Q10 of 14.5. Restoring the temperature to 24 degrees C decreased I(Ca) with a Q10 of only 2.4. The marked difference in the Q10 values indicated that late I(Ca) (pMg = 5-6) is an irreversible phenomenon. Phosphorylation suppressed the intracellular [Mg2+] dependency of late I(Ca). This effect of phosphorylation together with the inhibitory action of GTP(i) on Mg2+-dependent blocking of I(Ca) are common properties of mammalian and amphibian cardiomyocytes.

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منابع مشابه

Temperature-sensitive intracellular Mg block of L-type Ca channels in cardiac myocytes

Yamaoka, Kaoru, Tsunetsugu Yuki, Kayoko Kawase, Makoto Munemori, and Issei Seyama. Temperature-sensitive intracellular Mg2 block of L-type Ca2 channels in cardiac myocytes. Am J Physiol Heart Circ Physiol 282: H1092–H1101, 2002. First published November 1, 2001; 10.1152/ajpheart.00585.2001.—We examined the concentration-dependent blocking effects of intracellular Mg2 on Ltype Ca2 channels in ca...

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عنوان ژورنال:
  • American journal of physiology. Heart and circulatory physiology

دوره 282 3  شماره 

صفحات  -

تاریخ انتشار 2002