Effect of L-triiodothyronine on liver microsomal delta 6 and delta 5 desaturase activity of male rats.
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 micrograms T3/100 g body wt. for 5 days, whereas with 500 micrograms T3/100 g body wt. only delta 6 desaturase activity was decreased. On the other hand, no enzyme activity changed 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.
Ves-Losada
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Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), CONICET-UNLP, Facultad de Ciencias Médicas, Argentina.
Peluffo
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D000818:Animals; D000090943:Delta-5 Fatty Acid Desaturase; D044943:Fatty Acid Desaturases / Q000378:metabolism*; D050602:Linoleoyl-CoA Desaturase; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects* / Q000201:enzymology; D051381:Rats; D017208:Rats, Wistar; D014284:Triiodothyronine / Q000494:pharmacology*
D000090943:Delta-5 Fatty Acid Desaturase; D014284:Triiodothyronine; D044943:Fatty Acid Desaturases; D050602:Linoleoyl-CoA Desaturase