Abstract
Blood flow through interscapular brown adipose tissue and white epididymal or perirnetrial fat was estimated by the Sapirstein's radioactive isotope indicator method in the rat. Chronic cold exposure at 4-5°C for 2 weeks as well as acute exposure at 3°C for 30min resulted in a marked increase in the blood flow in brown adipose tissue, 14.7-fold and 2.8-fold respectively, while no significant effect was observed in the white adipose tissue.
Intravenous infusion of norepinephrine (2μg/min for 10min) into normal rats produced 6.4-fold increase in the blood flow through brown adipose tissue. Hexamethonium bromide could not prevent the increase of blood flow through brown adipose tissue caused by acute cold exposure. In cold-acclimated rats the infusion of norepinephrine failed to produce further increase in the blood flow of brown adipose tissue.
Thyroidectomy, methylthiouracil treatment and adrenalectomy did not affect the response of blood flow through brown adipose tissue to acute cold exposure nor to norepinephrine infusion. Thyroidectomized and methylthiouraciltreated rats failed to respond to chronic cold exposure in increasing the blood flow through brown adipose tissue.
