The concentration of uncoupling protein correlates with Mg2+ activated mitochondrial binding of GDP.
Rats were housed at 4 degrees C for periods of up to 26 days. As little as 2 h of cold exposure caused an increase in the binding of [3H]GDP to mitochondria from brown adipose tissue. Incubation of mitochondria in vitro with 10 mM Mg2+ caused a marked increase in the subsequent binding of GDP to mitochondria from rats housed at 28 degrees C and a smaller increase in that from rats exposed to 4 degrees C for 2 h. Chronic exposure to cold led to an even greater increase in the amount of GDP bound to mitochondria incubated with Mg2+. The time course for the increase in the concentration of uncoupling protein was compared with that for GDP binding to mitochondria with and without Mg2+ treatment. The concentration of uncoupling protein appears to be correlated with the GDP-binding values for mitochondria treated with Mg2+ (r = 0.70) but not with the GDP binding to untreated mitochondria (r = 0.36). Therefore, the binding of GDP to untreated mitochondria may represent thermogenic activity at the time of death, whereas that after treatment with Mg2+ may more closely reflect total thermogenic capacity of the mitochondrion.
Henningfield
M F
MF
Department of Nutritional Sciences, University of Wisconsin--Madison 53706.
Swick
R W
RW
D002001:Adipose Tissue, Brown / Q000378:metabolism; D000818:Animals; D002352:Carrier Proteins; D003080:Cold Temperature; D006150:Guanine Nucleotides / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000378:metabolism*; D007473:Ion Channels; D008274:Magnesium / Q000494:pharmacology*; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins; D051381:Rats; D011919:Rats, Inbred Strains; D000071256:Uncoupling Protein 1
D002352:Carrier Proteins; D006150:Guanine Nucleotides; D007473:Ion Channels; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D000071256:Uncoupling Protein 1; D006153:Guanosine Diphosphate; D008274:Magnesium