The development of lipid metabolism. Effect of short-term application of thyroxine on the level of fatty acids and albumin in serum during ontogenesis in rat.

ABSTRACT

In young rats of different age the effect of short-term administration of thyroxine (T4) on the level of 6 FFA was determined. The concentration of FFA was expressed in mmol/l as well as the molar ratio to serum albumin. The results show that the level of the total FFA and the ratio of saturated to unsaturated (S/U) FFA are high in control animals till the age of 21 days in comparison with adult animals. Administration of T4 caused marked increase in the total FFA in the youngest age group (8-day-old) and the effect increased with age. Differences in the trend of changes in individual FFA were found. In the concentration of myristic acid (C 140) a significant increase was found only till the age of 16 days; in the case of palmit-oleic acid the increase was significant in all age groups. T4 caused no significant changes in the values of stearic acid (180). When the data were expressed in terms of the molar ratio FFA/albumin, the changes were more pronounced. The peak values found in 16-day-old animals were 33.9 +/- 0.75; they represent a 2-times higher supply of FFA to tissues in comparison with control animals. In this study it was also found that the concentration of serum albumin in newborn animals is low and represents just 57% of adult values. The short-term application of T4 caused no changes in the concentration of serum albumin. The mechanism of T4 action on FFA during ontogenesis was not explained in this study.(ABSTRACT TRUNCATED AT 250 WORDS)