AJP - Cell Physiology, Vol 264, Issue 1 C217-C228, Copyright © 1993 by American Physiological Society

ARTICLES

Adrenergically activated Ca2+ increases in brown fat cells: effects of Ca2+, K+, and K channel block

S. C. Lee, R. Nuccitelli and P. A. Pappone
Department of Animal Physiology, University of California, Davis 95616.

We measured intracellular calcium concentration ([Ca2+]i) during adrenergic stimulation using fura-2 ratio imaging of individual cultured neonatal rat brown fat cells. One micromolar norepinephrine (NE) increased [Ca2+]i from an average resting value of 105 nM to 555 nM in approximately 30 s. [Ca2+]i remained elevated as long as NE was present but returned to resting levels within 2-3 min after NE removal. The response was half maximal at approximately 50 nM NE and was primarily alpha-adrenergic. The sustained, but not the initial, increase in [Ca2+]i required extracellular calcium. Cells stimulated in high-K media had [Ca2+]i responses like those in 0 Ca2+, suggesting that depolarization abrogates calcium influx. Parallel perforated-patch recordings showed that the increase in [Ca2+]i activates a calcium-activated K conductance. Blocking K channels with moderate concentrations of tetraethylammonium (TEA) had only small effects on NE-induced changes in [Ca2+]i, but high concentrations of TEA significantly reduced the response. We conclude that cytoplasmic calcium is modulated by fluxes from both intracellular and extracellular sources and that K channels may not be required for normal short-term [Ca2+]i responses to hormone.

This article has been cited by other articles:

				M. Kuba, Y. Higure, H. Susaki, R. Hayato, and K. Kuba Bidirectional Ca2+ coupling of mitochondria with the endoplasmic reticulum and regulation of multimodal Ca2+ entries in rat brown adipocytes Am J Physiol Cell Physiol, February 1, 2007; 292(2): C896 - C908. [Abstract] [Full Text] [PDF]

				S. M. Wilson, S. C. Lee, S. Shook, and P. A. Pappone ATP and beta -adrenergic stimulation enhance voltage-gated K current inactivation in brown adipocytes Am J Physiol Cell Physiol, December 1, 2000; 279(6): C1847 - C1858. [Abstract] [Full Text] [PDF]

				A. Koivisto, D. Siemen, and J. Nedergaard Norepinephrine-induced sustained inward current in brown fat cells: alpha 1-mediated by nonselective cation channels Am J Physiol Endocrinol Metab, November 1, 2000; 279(5): E963 - E977. [Abstract] [Full Text] [PDF]

				G. E. Bronnikov, S.-J. Zhang, B. Cannon, and J. Nedergaard A Dual Component Analysis Explains the Distinctive Kinetics of cAMP Accumulation in Brown Adipocytes J. Biol. Chem., December 31, 1999; 274(53): 37770 - 37780. [Abstract] [Full Text] [PDF]

				J. Zhao, B. Cannon, and J. Nedergaard alpha 1-Adrenergic Stimulation Potentiates the Thermogenic Action of beta 3-Adrenoreceptor-generated cAMP in Brown Fat Cells J. Biol. Chem., December 26, 1997; 272(52): 32847 - 32856. [Abstract] [Full Text] [PDF]

				E. V. Leaver and P. A. Pappone beta -Adrenergic potentiation of endoplasmic reticulum Ca2+ release in brown fat cells Am J Physiol Cell Physiol, May 1, 2002; 282(5): C1016 - C1024. [Abstract] [Full Text] [PDF]