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Transport of 3-hydroxybutyrate by cultured rat brain astrocytes
Authors:J Tyson Tildon PhD  Mary C McKenna  Joseph H Stevenson Jr
Institution:(1) Department of Pediatrics, University of Maryland School of Medicine, Room 10-033, BRB, 655 W. Baltimore Street, 21201 Baltimore, Maryland;(2) Department of Biological Chemistry, University of Meryland School of Medicine, Room 10-033, BRB, 655 W Baltimore Street, 21201 Baltimore, Maryland
Abstract:It is well established that 3-hydroxybutyrate can serve as an energy source for the brain. Since substrate utilization may be regulated in part by transport across the cellular membrane, we investigated the uptake of 3-hydroxybutyrate by primary cultures of rat brain astrocytes. Measurement of the net uptake indicated a saturable system and a Lineweaver-Burke type plot was consistent with a single carrier-mediated mechanism with a Km of 6.03 mM and a Vmax of 32.7 nmol/30 seconds/mg protein. The rate of uptake at pH 6.2 was more than ten times the rate at pH 8.2, with the rate at pH 7.4 being intermediate between these values, suggesting the possibility of cotransport with H+ or exchange with OH (antiport). Mersalyl had only a slight effect on the transport of 3-hydroxybutyrate, suggesting that sulfhydryl groups are not involved in the transport of this monocarboxylic acid. Phenylpyruvate and agr-ketoisocaproate also attenuated the transport, but lactate had only a marginal effect. These results suggest that the utilization of 3-hydroxybutyrate as an energy source by astrocytes is regulated in part by carrier-mediated transport and that the uptake system is different from the lactate transport system.These data were presented in part at the FASEB Meeting, April, 1990
Keywords:3-Hydroxybutyrate  transport  astrocytes  energy metabolism  brain cells
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