116: Comparative turnover rates of free fatty acids |[sol]|FFA|[sol]| and free glycerol in blood of newborn rabbits

摘要

Determination of tracer kinetic patterns of circulating FFA and free glycerol might be of value in the elucidation of their metabolic pathways and their quantitative contribution to the calorigenesis in the main heat producing organs and tissues of the newly born.After i.v. injection of 14C-1-palmitate or 14C-l,3-glycerol /20.10 d.p.m./100 g bwt/ the turnover rate of plasma FFA and free glycerol was found 10,2 and 0,85 μmol/min/100 g bwt respectively in a thermoneutral environment of 35°C /T 35°C/. Exposure to cold /Ta 20°C/ caused a decrease in FFA turnover /5,84 μmol/min/ and an increase in free glycerol turnover /2,45 μmol/min/. The plasma concentrations of both metabolites increased significantly during cold exposure /FFA from 0,403+ 0,041 to 0,518±0,057; free glycerol from 0,251±0,021 to 0,505±0,057/. These findings indicate that during cold-induced calorigenesis in the newborn rabbit substantial part of stored fatty acids are oxidized in brown adipose tissue itself, while the bulk of the concomitantly produced glycerol is being released into the circulation resulting in a ratio of FFA: glycerol turnover of 2,4 : 1. It practically means that in the bold during hydrolysis of adipose tissue triglycerides instead of 3 only 2,4 moles of FFA entered and left the blood for each bole of glycerol.