Effect of L-triiodothyronine on liver microsomal D6 and D5 desaturase activity of male rats

VES-LOSADA, ANA; PELUFFO RAúL O.

MOLECULAR AND CELLULAR BIOCHEMISTRY

Kluwer Acad. Publishers

Año: 1993 vol. 121 p. 149 - 153

0300-8177

The effect of different doses of L-triiodothyronine (T3) on the activity of  delta 6 and delta 5 desaturases and lipid fatty acid composition was studied in liver microsomes of male rats. The activity of delta 6 and delta 5 desaturases was decreased 24 and  28%, respectively, in animals administered a daily intraperitoneal dose of 1000 ìg t3/100g body wt for 5 days, whereas with 500 ìg T3/100 g body wt only delta 6 desaturase activity was decreased. On the other hand, no enzyme activity changes at a shorter period of hormone treatment. Changes in microsomal fatty acid composition did not seem to be a direct consequence of desaturation activity, since after 1 and 5 days of T3 treatment, the concentrations of 18:2 (n-6) and 20:3 (n-6) decreased and only after 1 day that of 20:4 (n-6) increased in spite of unchanged or decreased delta 6 and delta 5 desaturase activities. Other factors than desaturation activity must be involved in fatty acid composition of thyroid hormone-treated rats, such as diet, membrane lipid synthesis and degradation, fatty acid turn-over and oxidation .