alpha 1-Adrenergic activation of isolated brown adipocytes causes a rapid mobilization of intracellular Ca2+. The cells also respond with an increased turnover of inositol lipids. The present work demonstrates that alpha 1-adrenergic stimulation of brown adipocytes results in phospholipase C-mediated breakdown of phosphatidylinositol bisphosphate to form inositol trisphosphate. The rate of appearance of inositol trisphosphate is sufficiently rapid for it to mediate or contribute to Ca2+ mobilization in these cells.
This work was supported by NIH grants nos DE-05764 and AM-32823. E.N. was the recipient of grants from Åqvists fond and Wallenbergs Jubileumsfond and of support from Magnus Bergvalls Stiftelse and The Swedish Natural Science Research Council (to Barbara Cannon and Jan Nedergaard).