Possible role of polyamines in the function of brown adipose tissue.

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Abstract
To ascertain involvement of polyamines in the physiological regulation of brown fat function, effect of temperature acclimation on the polyamine contents of this tissue and effects of polyamines on the noradrenaline[norepinephrine]-induced thermogenesis of isolated brown adipocytes were investigated in rats. Daily urinary excretion of polyamines measured collectively for spermidine and spermine per body weight was decreased in heat acclimation and increased in cold acclimation. Polyamine concentrations per fresh weight of brown fat showed extremely low values compared with those of other tissues previously reported. Putrescine and spermidine contents per fat-free dry matter of brown fat were decreased in cold acclimation, but were not affected in heat acclimation. Spermidine and spermine inhibited the noradrenaline-induced thermogenesis of brown adipocytes dose-dependently. Polyamines apparently regulate the heat production of brown adipose tissue in an inhibitory way; cold acclimation potentiates heat production of this tissue by reducing polyamine levels.