Effects of alpha-methyl-p-tyrosine and cold stress on tissue norepinephrine, plasma NFFA, glucose and colonic temperature in warm- and cold-acclimated rats

Abstract

The increase in urinary catecholamine in the animals subjected to cold has been observed by many authors. Also it is demonstrated by several investigators that norepinephrine (NE) and epinephrine (E) released from sympathetic nervous system and adrenal glands produced an increase in plasma NEFA and glucose as fuels. This experiment dealt with the effects of a tyrosine hydroxylase inhibitor, α-methyl-p-tyrosine (α-MPT) and of cold stress on tissue NE, plasma NEFA, glucose and colonic temperature in warm- and cold-acclimated rats to investigate the physiological significance of sympathetic nervous system in the regulation of metabolism for maintaining their body temperature. In rats exposed to cold for 4 weeks, the utilization of heart NE is accelerated during the first week. After cold-acclimation has been accomplished, it appears that NE utilization is decreased. Under such experimental conditions it appears that NEFA and glucose play a compensatory role for maintaining body temperature and that plasma glucose acts as a more effective energy source in withstanding cold stress than plasma NEFA. This experiment suggests that after adult control rats (wt. approx. 300 gr) had been subjected to severe cold stress for several hr, the pattern of biosynthesis and utilization of catecholamine in vivo, did not differ greatly from those of the cold-acclimated rats.