RESUMEN
Cold acclimatization (4-5ºC) is accompanied by 2-3 fold increase of brown adipose tissue (BAT). This rapid growth of interscapular BAT was studied after histamine depletion. In control rats maintenained at room temperature (28 ñ 2ºC) the BAT histamine content was 23.4 ñ 5.9 (mean ñ SD) µg/g of tissue and cold acclimatization (5 ñ 1ºC) produced a signifacant increase of BAT weight, but reduced the histamine content to 8.4 ñ 1.9 µg/g. The total weight of BAT after 20 days of acclimatization was unaffected by depletion of histamine due to compound 48/80. The low level of histamine in BAT of cold acclimatization rats could be a fast rate of amine utilization; alternatively and altered synthesis or storage process may occur during acclimatization.