Uptake and incorporation of arachidonic acid and of dihomogamma-linolenic acid into tissue lipids in uterine strips isolated from ovariectomized and from ovariectomized-diabetic rats. Effects of 17-beta-estradiol

Abstract

The uptake of 14C-arachidonic acid ( 14C-AA) and 14C-dihomogamma-linolenic acid ( 14C-DGLA) into phospholipids (PLs) and neutral lipids (NLs) in uterine tissue obtained from ovariectomized controls (C) and from ovariectomized-diabetic rats (D) was studied. Uterine strips from D rats incorporate significantly less (P<0.05) 14C-AA into PLs than C rats. On the other hand the uptake of 14C-AA into NLs is significantly smaller (P<0.05) in uterine tissue from C than from D animals. The estrogenization of the C animals did not modify the incorporation of 14C-AA into PLs or NLs. On the contrary, uterine tissue obtained from D rats treated with 17-beta-estradiol incorporated significantly more labelled AA (P<0.05) into PLs and significantly less 14C-AA (P<0.05) into NLs than untreated D animals. The incorporation of 14C-DGLA into PLs shows similar pattern in uterine tissue obtained from C and D animals. Estrogenization increased significantly (P<0.01) in both cases, the incorporation into PLs. Regarding the incorporation of 14C-DGLA, it was clearly shown that DGLA is taken up significantly more (P<0.01) by NLs than by PLs, both in C and D rats. The estrogenization of C and D rats induces a significant decrease in the incorporation of 14C-DGLA into NLs in both experimental groups. The distribution of 14C-AA into the different subfractions of PLs is not uniform. Indeed, 14C-AA is taken up significantly more by phosphatidylinositol (PI) than by phosphatidylcholine (PC) in C group, but this difference is not seen in the uterine tissue from D rats. On the other hand, estradiol treatment induced a redistribution of this labelled fatty acid into the different subfractions of PLs in C and D rats. The incorporation of 14C-DGLA into different types of PLs is similar in uterine segments from C and D rats, nevertheless, the stimulating action of estradiol on the incorporation of 14C-DGLA into the PLs subfractions is different in C and in D rats, i.e. uterine tissue obtained from C rats incorporate more 14C-DGLA into PI than into PC, whereas in uterine tissue from D rats, the incorporation was higher in PC than in PI. The interpretation of the present results and the possible implication of the acylation/deacylation cycle of these unsaturated fatty acids in the synthesis of PGs is discussed.