Relationship between global cytosolic Ca2+ concentration and Ca2+- activated K+ current in rabbit cerebral arterial myocyte

Joon Kim Sung Joon Kim, Mo Ahn Joong Mo Ahn, Chul Kim Young Chul Kim, S. J. Park, Young Choi Jae Young Choi, Hyo Suh Suk Hyo Suh, I. So, Whan Kim Ki Whan Kim

Research output: Contribution to journalArticle

Abstract

In smooth muscle cells, the sarcoplasmic reticulum (SR) has been identified as the primary storage site for intracellular Ca2+. The peripheral SR is in close proximity with plasma membrane to make a narrow subsarcolemmal space. In this study, we investigated the regulation of subsarcolemmal [Ca2+] ([Ca2+](s1)) and global cytosolic [Ca2+] ([Ca2+](c)) of rabbit arterial smooth muscle using whole-cell patch clamp technique and microspectrofluorimetry. The Ca2+-activated K+ current (I(K(Ca))) and the ratio of fura-2 fluorescence (R(340/380)) were considered to reflect the [Ca2+](s1) and [Ca2+](c), respectively. At a holding potential of 0 mV, extracellular application of 10 mM caffeine, a well-known Ca2+-releasing agent, induced transient increase of I(K(Ca)) and R(340/380) (I(K(Ca))-transient and R(340/380)-transient, respectively). The increase and decay of I(K(Ca))-transient was faster than R(340/380)-transient. By repetitive application of caffeine, when the refilling state of SR was supposed to be lower than the control condition, I(K(Ca))-transient and R(340/380)-transient were suppressed to different levels; e.g. the second application 20 sec after the first could induce smaller I(K(Ca))-transient than R(340/380)-transient. Dissociation of I(K(Ca))-transient and R(340/380)- transient was removed by sufficient (>3 min) washout of caffeine. Recovery from the dissociation was also dependent upon the membrane potential; faster recovery was observed at negative (-40 mV) holding potential than at depolarized (0 mV) condition. Dissociation of I(K(Ca)) from [Ca2+](c) was also partially prevented by perfusion with Na+-free (replaced by NMDG+) extracellular solution. These results suggest that, 1) there is prominent spatial inhomogeneity of [Ca2+] in cerebral arterial myocyte, 2) [Ca2+](s1) is preferentially affected by the interference from nearby plasmalemmal Ca2+ regulation mechanism which is partly dependent upon extracellular Na+.

Original languageEnglish
Pages (from-to)159-172
Number of pages14
JournalJournal of Smooth Muscle Research
Volume34
Issue number4
StatePublished - 1 Dec 1998

Keywords

  • Ca concentration
  • Ca-activated K current
  • Smooth muscle

Cite this

Sung Joon Kim, J. K., Joong Mo Ahn, M. A., Young Chul Kim, C. K., Park, S. J., Jae Young Choi, Y. C., Suk Hyo Suh, H. S., So, I., & Ki Whan Kim, W. K. (1998). Relationship between global cytosolic Ca2+ concentration and Ca2+- activated K+ current in rabbit cerebral arterial myocyte. Journal of Smooth Muscle Research, 34(4), 159-172.