Angkanaporn, K., Ravindran, V., Mollah, Y. and Bryden, W.L., 1997. Secretion of homoarginine into the gut of chickens. Veterinary Research Communications, 21(3), 161-167A technique, based on the homoarginine present in guanidinated proteins, has been used to distinguish between endogenous secretions and exogenous dietary amino acids in the ileal digesta of monogastric animals. This technique assumes that the ingested homoarginine is not recycled into the small intestine after absorption, but this assumption is yet to be experimentally validated in chickens. The secretion of homoarginine into the gut of broilers that were intravenously infused with 20 and 40 mmol/L homoarginine solutions was assessed. The plasma concentrations of homoarginine increased with increasing concentrations of homoarginine infused. However, only negligible levels of homoarginine (7.0 to 45.2 µg/g dry matter) were found in the digesta. Less than 0.01% of the intravenously infused homoarginine was recovered in the intestinal digesta, indicating that the secretion of homoarginine into the gut of chickens was insignificant. 相似文献
1. The influence of caecectomy and dietary crude protein content (50, 100, 150, 200 and 250 g/kg diet) on the apparent excreta amino acid digestibilities in adult cockerels fed on semi‐purified diets containing soyabean meal (SBM) or cottonseed meal (CSM) as the sole source of protein was investigated.
2. Caecectomy had no influence on the apparent digestibilities of most amino acids in SBM, the exceptions being histidine, arginine and lysine, but lowered the apparent digestibility of amino acids in CSM.
3. The protein content in assay diets has a strong influence on the apparent amino acid digestibility values for poultry. Apparent values are lower when the dietary protein content is low.
4. The use of a single endogenous amino acid output value, generated by regression analysis or protein‐free diets, for true digestibility adjustments across a wide range of protein intakes is questioned. In particular, such an application will penalise estimates of apparent digestibility when the dietary protein content is high. 相似文献
1. Endogenous amino acid losses in ileal digesta and excreta of adult cockerels fed on diets containing guanidinated forms of casein, soyabean meal and cottonseed meal were determined using homoarginine as a marker.
2. The ileal endogenous amino acid losses were markedly higher (P< 0–001) in birds given the cottonseed meal diet compared to those given the other two diets. The ileal endogenous protein was rich in aspartic acid, serine and glutamic acid.
3. Negative values were obtained for endogenous amino acid output in excreta. These aberrant values were caused by high concentrations of homoarginine in the excreta. A subsequent study with broiler chickens showed that the homoarginine in excreta was of urinary origin.
4. These results indicate that the homoarginine technique is not suitable for determining endogenous amino acid losses in excreta, but applicable when determinations are made in the terminal ileum. 相似文献
We studied whether the effects of bethanechol are mediated via a muscarinic receptor, the role of extracellular calcium on bladder contraction, and down-regulation of bladder contraction by bethanechol after activation with potassium chloride (KCl) and acetylcholine (Ach). Smooth muscle strips of normal urinary bladder were studied with standard methods to measure isometric force. Bethanechol caused a dose-dependent increase in bladder contraction. The potency of bethanechol is higher than Ach, as shown by higher peak active isometric stress (P(max)) and lower half-maximal contraction (ED(50)) (P< 0.01). The contractile responses to bethanechol were diminished in the presence of atropine, nifedipine and in calcium-free medium as shown by P(max) decreased by 58%, 87% and 65% and ED(50) increased by 314-, 24- and 16-fold, respectively. When bladder strips were stimulated with KCl and Ach, pre-treatment with bethanechol reduced the responses to KCl by 116-242% (P<0.05), while the contractile responses to Ach were unaltered. Thus, bethanechol induces bladder contraction via muscarinic receptor activation while both intracellular and extracellular calcium play a crucial role on bladder smooth muscle contraction. The mechanisms of down-regulation by bethanechol may be related to interference with calcium influx into the smooth muscle cells, rather than the desensitisation of muscarinic receptors or post-receptor steps of signal transduction following bethanechol binding to the receptor. 相似文献
