TY - JOUR
T1 - Insulin regulation of lipoprotein lipase in cultured isolated rat adipocytes
AU - Eckel, Robert H.
AU - Prasad, Judith E.
AU - Kern, Philip A.
AU - Marshall, Stephen
PY - 1984
Y1 - 1984
N2 - The cellular regulation of adipose tissue lipoprotein lipase by insulin was investigated using cultured isolated rat adipocytes. Evidence for sustained cell viability over 3 days included stability of specific [125I]insulin binding and adipocyte number. Lipoprotein lipase was measured in three functional compartments: 1) enzyme activity secreted into the culture medium, 2) activity releasable from cell suspensions by heparin, and 3) activity extractable from cells (after maximal heparin release) in deoxycholate and detergent. One day after preparation, these activities stabilized and were 1.3 ± 0.2,1.4 ± 0.2, and 7.7 ± 0.9 neq/106 cells min, respectively (n = 24, mean ± SEM). Insulin, added the day after preparation, produced a dose-dependent (1-400 ng/ml) increase in lipoprotein lipase releasable from cells by heparin at 2, 4, and 24 h. Insulin also increased intracellular enzyme measured as deoxycholate-detergent-solubilized activity extracted from previously heparin-released cells. However, insulin-mediated increases in culture medium enzyme only occurred subsequent to cellular effects. All insulin-mediated effects were prevented by cycloheximide (1 µg/ml). Thus, insulin increased two cellular pools of adipocyte lipoprotein lipase in a dose-dependent manner, but had no direct effect on enzyme secretion. Overall, cultured isolated rat adipocytes appear to be a valuable system for the study of lipoprotein lipase regulation at the level of the adipocyte.
AB - The cellular regulation of adipose tissue lipoprotein lipase by insulin was investigated using cultured isolated rat adipocytes. Evidence for sustained cell viability over 3 days included stability of specific [125I]insulin binding and adipocyte number. Lipoprotein lipase was measured in three functional compartments: 1) enzyme activity secreted into the culture medium, 2) activity releasable from cell suspensions by heparin, and 3) activity extractable from cells (after maximal heparin release) in deoxycholate and detergent. One day after preparation, these activities stabilized and were 1.3 ± 0.2,1.4 ± 0.2, and 7.7 ± 0.9 neq/106 cells min, respectively (n = 24, mean ± SEM). Insulin, added the day after preparation, produced a dose-dependent (1-400 ng/ml) increase in lipoprotein lipase releasable from cells by heparin at 2, 4, and 24 h. Insulin also increased intracellular enzyme measured as deoxycholate-detergent-solubilized activity extracted from previously heparin-released cells. However, insulin-mediated increases in culture medium enzyme only occurred subsequent to cellular effects. All insulin-mediated effects were prevented by cycloheximide (1 µg/ml). Thus, insulin increased two cellular pools of adipocyte lipoprotein lipase in a dose-dependent manner, but had no direct effect on enzyme secretion. Overall, cultured isolated rat adipocytes appear to be a valuable system for the study of lipoprotein lipase regulation at the level of the adipocyte.
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U2 - 10.1210/endo-114-5-1665
DO - 10.1210/endo-114-5-1665
M3 - Article
C2 - 6370664
AN - SCOPUS:0021368646
SN - 0013-7227
VL - 114
SP - 1665
EP - 1671
JO - Endocrinology
JF - Endocrinology
IS - 5
ER -