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Biomedical subjects

S F Phillips

Publications and source records attributed to S F Phillips.

At least 235 records · Page 13Linked to original sources
PubMed1974

Inhibition of ileal water absorption by intraluminal fatty acids. Influence of chain length, hydroxylation, and conjugation of fatty acids.

The influence of fatty acids on ileal absorption of water, electrolytes, glucose, and taurocholate was examined in Thirty-Vella fistulas in five mongrel dogs. Fatty acid absorption also was measured. Segments of terminal ileum were perfused at steady state with isotonic electrolyte solutions containing 11.2 mM glucose, 4.5 mM taurocholate, and 0.1-5.0 mM fatty acid. Three C(18) fatty acids, oleic acid, 10(9)-hydroxystearic acid, and ricinoleic acid, completely inhibited water absorption at 5 mM. Sodium, chloride, and potassium absorptions were inhibited in parallel with absorption of water. Differences between the potencies of C(18) fatty acids were apparent when lesser concentrations were perfused. Dodecanoic and decanoic acids were as effective as C(18) fatty acids at 5 mM but octanoic and hexanoic acids were ineffective. The polar group of C(18) fatty acids was modified by conjugating oleic and ricinoleic acids with taurine. When these compounds and a substituted C(18) fatty acid, p-n-decylbenzenesulfonate, were perfused, water absorption was also inhibited. Short-chain fatty acids (C(3) and C(4)) and their hydroxylated derivatives were ineffective at 5 mM. When water absorption was inhibited, absorption of glucose and taurocholate was decreased. We speculate that the phenomenon of inhibition of water and electrolyte absorption by fatty acids may be relevant to steatorrhea and diarrhea in man.

Animals↗
PubMed1974

Effects of oleic and ricinoleic acids on net jejunal water and electrolyte movement. Perfusion studies in man.

To examine the effects of oleic acid and ricinoleic acid on jejunal absorption, steady-state jejunal perfusions were performed in healthy volunteers. Taurocholate, used to solubilize the fatty acids, did not influence absorption. Both fatty acids (concentration, 10 mM) reversed electrolyte and water net movement; that is, they induced fluid secretion; this effect was rapidly reversible. Ricinoleic acid (the active principle of castor oil) was the more potent, producing fluid secretion when perfused at concentrations at which oleic acid was without effect. However, ricinoleic acid was absorbed more slowly than was oleic acid, and hence was associated with higher intraluminal concentrations. Addition of lecithin and monoolein did not diminish the secretory effect of ricinoleic acid; addition of a secretory bile acid (taurodeoxycholate) did not enhance the effect. The response of the jejunal mucosa to a known cathartic provides observations pertinent to the pathophysiology of steatorrheal diseases in man. Dietary fatty acid also has secretory properties with respect to the human intestine; bacterial hydration, to hydroxy fatty acids, is not required to induce fluid secretion.

Body Water↗
PubMed1974

Active and passive bile acid absorption in man. Perfusion studies of the ileum and jejunum.

Absorption of the major human bile acids was studied in 12 healthy volunteers by steady state perfusion of the ileum in 112 experiments and of the jejunum in 48 experiments. Use of a randomized order of four perfusions on 1 day of study and use of up to 4 consecutive days of study in a subject allowed important comparisons of data from the same individuals. That there is active ileal absorption of chenodeoxycholic, glycochenodeoxycholic, and taurocholic acids in man was supported by the finding of saturation kinetics and of competition for absorption among conjugated bile acids. Values for apparent kinetic constants (apparent maximal transport velocity [(*)V(max)] and apparent Michaelis constant) in man are similar to those in other species. The ileum absorbed chenodeoxycholic acid more rapidly than its glycine conjugate, due mainly to a ninefold greater permeability for the free acid. Taurocholate had the highest (*)V(max) and was absorbed more rapidly than glycochenodeoxycholate. Passive permeability of the jejunum to bile acids was twice that of the ileum, and the permeabilities to free and glycine-conjugated chenodeoxycholate were in the same ratio as in the ileum (9: 1). Jejunal permeability to chenodeoxycholic acid was three times that to cholic acid. Variation of intraluminal pH by up to 1.4 units did not influence jejunal uptake of free bile acids. These results, which are comparable with those from animal experiments, provide a basis for estimation of intestinal reabsorption of bile acids in intact man.

Adult↗
PubMed1973

Effect of glycine-conjugated bile acids with and without lecithin on water and glucose absorption in perfused human jejunum.

Perfusion studies were performed in healthy volunteers to test whether the secretory effect of conjugated bile acids, previously shown for the colon, was also present in the jejunum. A perfusion system with a proximal occlusive balloon (and continuous aspiration of duodenal secretions) was used; isotonic test solutions contained glycine-conjugated bile acids with or without lecithin. Fluid movement was measured by changes in the concentration of polyethylene glycol (PEG, mol wt 4,000). Conjugated dihydroxy bile acids inhibited electrolyte and fluid absorption and, at higher concentrations, evoked secretion of an isotonic fluid. Glucose absorption continued, despite fluid secretion, but its rate decreased. The secretory effects of bile acids were abolished by the addition of lecithin to the bile acid solutions. A trihydroxy bile acid (cholylglycine) had no effect on jejunal absorption. Small amounts (6-9%) of conjugated bile acids were absorbed in the jejunum; lecithin was well absorbed (72-90%). The results indicate that dihydroxy bile acids influence salt and water transport in the human jejunum but that this effect may be abolished when a polar lipid such as lecithin is present. We speculate that this effect of bile acids may modify fluid movement in the small intestine postprandially after fat absorption has occurred.

Bile Acids and Salts↗
PubMed1972

A comparison of stable and 14 C-labelled polyethylene glycol as volume indicators in the human jejunum.

Polyethylene glycol (PEG plus (14)C-PEG) was measured turbidimetrically and by liquid scintillation counting to compare the validities of these methods during the use of PEG as a volume indicator of intestinal perfusion studies in man. Use of (14)C-PEG results yielded similar estimates of water absorption or secretion. The simplicity of (14)C counting offers practical advantages to the use of (14)C-PEG as a nonabsorbable marker for perfusion studies in man.

Bile Acids and Salts↗