Sulfur and methionine metabolism in sheep. II. Quantitative estimates of sulfur metabolism in the sheep's stomach.

The metabolism of dietary and supplemental DL-methionine sulfur in the stomach of sheep was studied in two experiments. In both experiments sheep were fed a 50 : 50 oaten chaff: lucerne chaff ration at two levels of intake, and some animals received intraruminal infusions of DL-methionine. In experiment 2 increasing dry matter intake (DMI) increased first approximations of total, neutral, protein and reducible sulfur flows and also sulfide sulfur flow from the reticulo-rumen. Increased DMI (from 500 to 1000 g/day) also resulted in greater true flows of total (2207 v. 1104 mg/day), neutral (1867 v. 1043 mg/day) and protein (893 v. 482 mg/day) sulfur at the duodenum. Two flow diagrams of sulfur metabolism in the compartments of the ruminant stomach were developed from the data of experiment 2. Fluid flows of sulfur in experiment 1 were used to supplement the data of experiment 2 in developing the balance models. The two models represent the extremes of dietary and supplemental sulfur metabolism in the sheep's stomach under the conditions of experiment 2, and they are discussed in relation to previous research on sulfur metabolism in the stomach.     

Acute meal-induced changes in hepatic glycerolipid metabolism are unimpaired in severely diabetic rats: implications for the role of insulin

The effect of food intake on the partitioning of diacylglycerol between phospholipid and triacylglycerol synthesis, and on the fractional rate of secretion of triacylglycerol was studied in starved-refed diabetic rats by using the technique of selective labelling of hepatic fatty acids in vivo. Acute and phasic responses in these parameters similar to those observed previously in normal animals were obtained, in spite of the absence of any insulin response to refeeding. Labelling of the major phospholipids (phosphatidylcholine and phosphatidylethanolamine) increased markedly at the expense of triacylglycerol labelling. In addition, the fractional rate of secretion of newly-labelled triacylglycerol was decreased. The data suggest that insulin is not obligatorily involved in any decreases in hepatic triacylglycerol secretion in the prandial period, but that it may act synergistically with other meal-induced signals to mediate this effect in normal animals.