THE LYMPHATIC ABSORPTION OF FATTY-ACIDS AND OUTPUT OF PHOSPHOLIPIDS ARE LOWERED BY ESTROGEN REPLACEMENT IN OVARIECTOMIZED RATS

The lymphatic absorption of fatty acids and output of lipids during in traduodenal lipid infusion were compared in Sprague-Dawley ovariectomi zed rats with (OXE) and without (OXP) estradiol implants. A time-relea se estradiol pellet (25 mu g/day/rat) was implanted subcutaneously in the OXE rats and a placebo pellet in OXP rats. At 4 weeks, rats were f itted cannula and infused at 3.0 ml/hr via a duodenal catheter with a lipid emulsion containing 3.2 mu Ci C-14-linoleic acid (C-14-La), 171 mu mol LA, 488 mu mol triolein, 520 mu mol sodium taurocholate, and 1. 5 mu mol alpha-tocopherol in 24 ml phosphate buffered saline (pH 6.4). Lymph was collected at hourly intervals for 8 hours via a mesenteric lymph cannula. The average rate of lymph flow was reduced in OXE (1.4 ml/hr), compared with that of OXP rats (2.2 ml/hr). The total cumulati ve absorption of C-14-LA during the 8-hr period, as expressed in % dos e, was significantly lower in OXE (26.9 +/- 5.2%) than in OXP rats (33 .6 +/- 4.0%). The lymphatic outputs of fatty acids (16:0, 18:0, 18:1, 18:2, and 18:3) also were significantly reduced in OXE rats. The amoun t of 14C-LA absorbed into the lymph were high correlated (r = 0.85, P < 0.05) with the amount of phospholipid (PL) released. The results pro vide the first evidence that the rate of lymphatic absorption of lipid s is reduced by estrogen replacement in ovariectomized rats. This may be caused by a limited availability of PL to the enterocyte during chy lomicron formation.