Insulin activation of acetyl-CoA carboxylase in isolated mammary acini from lactating rats fed a high-fat diet

Abstract

the findings in absorptive conditions when this organ is actively taking up these compounds (Remesy et al., 1978; Pastor-Anglada & Remesar, 1986). In fact, some circadian variations in the Na+ -dependent amino acid transport capacity at the hepatic level have also been reported to occur (Bourdel & Forestier, 1982), probably in accordance with the portal amino acid supply. However, a 24 h starvation period induced a net uptake of essential amino acids, which was accounted for by peripheral sources, since the arterial levels were increased (1 350 f 70 PM versus 1 123 60 PM, P < 0.05) and there was a net splanchnic retention (1 I . 1 2.0% versus -3.9 f 4.4%, P < 0.05). This adaptation was mediated by a sharp increase in the relative hepatic fractional extraction rates (from -2.5 f 2.8% to 8.8 f 1.7%. P < 0.01) (Fig. 1). The fed postprandrial pregnant rats showed a net hepatic uptake of essential amino acids, mainly supported by the intestinal supply, showing a relative fractional extraction rate over 15.9 f 2.5% (P < 0.001 when compared with fed virgin controls). However, starvation failed to induce a further increase in this parameter (10.2 f 2.8%) conversely to what has been reported to occur in non-pregnant animals. Furthermore, also in the food-deprived pregnant animals the hepatic uptake was mediated by an intestinal efflux of essential amino acids. Thus, pregnant rats either fed or starved showed nil splanchnic balances for these amino acids (4.5 f 4.5% and 2.5 From these results it is clear that a different response to starvation occurs in the pregnant rats and that this response implies an amino acid-sparing mechanism in order to support the foetal development.