Studies on the effect of heat exposure on lipid metabolism in rat: Modifications of lipids in plasma, erythrocytes and liver

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

“…The results showed the elevated urinary excretion of polyamines in the coldacclimated rats and the reduced excretion in the heat-acclimated rats.It is well known that cold acclimation causes the increases in the weights of gut and liver (EMERY et al,1939;HEROUX and GRIDGEMAN,1958),where high concentrations of polyamines are found (JANNE et al,1964).Therefore,it is likely that the increased excretion of polyamines would have resulted from the increased mass of tissues containing large amounts of polyamines and/or increased formation of polyamines.Changes in polyamine synthesis are followed by corresponding changes in urinary excretion during pregnancy (ANDERSSON et al,1978;ROJANSKY et al,1979).On the other hand,heat acclimation results in suppressed thyroidal function (COLLINS and WEINER,1968),lessened growth (JOUANNETEAU and PERES, 1979;KUROSHIMA et al,1978)and reduced liver size (CHAYOTH et al,1977;JOUANNETEAU and PERES,1979).Ablation of thyroid gland decreases the hepatic polyamine concentration (HARIK,1979).Thus,it is inferred that the overall formation of polyamines is decreased in the heat-acclimated rats,resulting in the reduced excretion of urinary polyamines.…”