Fig. 6.
Time- and dose-dependent activation of LPA5 by mesenteric lymphatic fluid (MLF) that is a function of feeding. Lymphatic fluid was collected from rats with cannulated mesenteric lymphatic ducts after presentation of an intestinal 3-ml bolus of either dextrin as a control (1.1 g in 3 ml 0.9% NaCl) (n = 3), Liposyn, or Ensure, which is a mixed meal consisting of fat, carbohydrate, and protein. The MLF was used to determine LPA5 activation in an aequorin (AEQ)-based [Ca2+] assay. A: Chinese hamster ovary cells heterologously expressing LPA5 were treated with MLF (1:50 dilution) from dextrin-infused rats (n = 3) and Liposyn-infused (n = 3) rats. The activation of LPA5 by Liposyn-derived MLF showed significant enhancement over time, which peaked at 120 min. B: LPA5 activation displays a dose dependency on MLF from mix meal-treated animals. MLF was collected from rats with cannulated mesenteric lymphatic ducts 120 min after the presentation of an intestinal 3-ml bolus of Ensure. Changes in [Ca2+]i were determined by AEQ-based [Ca2+] assay (RLU, relative light units). Bars are means ± SD (n = 3). C: hBRIE380i cells heterologously expressing LPA5 were treated with MLF from rats with intact mesenteric lymphatic ducts (n = 4) or rats with diverted bile (-BD) (n = 4). MLF (1:5 dilution) significantly induced the mobilization of [Ca2+]i independent of the presence of bile. Bars are means ± SD. Values for each figure are significantly different than their respective controls at P < 0.05.