James Allen Olson

Action of bile salts on the metabolism and transport of water-soluble nutrients by perfused rat jejunum in vitro

Abstract The highly purified, crystalline conjugated bile salts glycocholate and taurocholate at 8 mM did not affect: (1) the transport of glucose, sorbose, urea, lysine, leucine, acetate and sodium across perfused segments of rat jejunum; (2) the incorporation of leucine and lysine into protein, or of acetate into lipid by perfused jejunal segments; or (3) the uptake of oxygen and the conversion of glucose into triglyceride by jejunal rings. However, they did inhibit adenosine triphosphate activity of jejunal mucosal homogenates and brush border preparations, and at 4 mM significantly decreased the P:O ratios of respiring liver mitochondria. Deoxycholate, a common contaminant of conjugated bile salt preparations, at 0.4 mM inhibited the transport of all substances examined, except sorbose, and depressed the other metabolic functions studied. Cholate was a weaker inhibitor than deoxycholate. Longchain fatty acids, another common contaminant of bile salt preparations, caused an increased incorporation of glucose into triglyceride. Thus previous reports that conjugated bile salts stimulate or inhibit the absorption or intracellular metabolism of water-soluble nutrients by the gut may well have resulted from contamination of the bile salt preparations with deoxycholate or fatty acids.

Retinoyl beta-glucuronic acid: a major metabolite of vitamin A in rat bile.

The major metabolite in rat bile of injected C14-retinoic acid was purified by ion-exchange and silicic acid chromatography; it has the spectrum of methyl retinoate, releases retinoic acid upon basic hydrolysis or by treatment with β-glucuronidase, and contains glucuronic acid. The metabolite was characterized by treatment with diazomethane followed by hexamethyl-disilazane, or with periodate followed by semicarbazide, and the products were chromatographed. The metabolite has been tentatively identified as retinoyl β-glucuronide.

INHIBITORY EFFECTS OF BILE ACIDS ON ADENOSINE TRIPHOSPHATASE, OXYGEN CONSUMPTION, AND THE TRANSPORT AND DIFFUSION OF WATER-SOLUBLE SUBSTANCES IN THE SMALL INTESTINE OF THE RAT.

Abstract Physiological concentrations of conjugated bile acids inhibit the active transport of sodium, adenosine triphosphatase, oxygen consumption, and the diffusion of sorbose and urea in the upper intestine of the rat, but do not affect the diffusion of urea in the ileum. A possible mechanism for the action of conjugated bile salts on the transport and metabolism of water-soluble nutrients in the intestine is suggested.

Spectrophotometric measurement of α-keto acid semicarbazones☆

Abstract The influence of hydrogen-ion concentration on the rate of formation of several α-keto acid semicarbazones has been investigated. General acid catalysis of the reaction was observed with monocarboxylic keto acids but not with the dicarboxylic acids, α-ketoglutarate and oxalacetate. Conditions have been defined for the simple rapid analysis of keto acid solutions, for the measurement of blood keto acid levels, and for the continuous spectrophotometric measurement of glyoxylate formation by isocitric lyase at pH 6. The advantages and limitations of the method are discussed.

The effect of diphenylamine on carotenoid, sterol and fatty acid synthesis in Phycomyces blakesleeanus.

Abstract In shake flask cultures of Phycomyces blakesleeanus , β-carotene increased proportionally with the dry weight of mycelium after a short lag. The relation among phytoene, β-carotene, and sterol remained constant during the early growth phase. In diphenylamine-treated cultures, phytoene increased greatly, β-carotene fell, ergosterol remained the same or increased slightly, and fatty acids remained constant. The incorporation of acetate-1-C 14 into these fractions was proportional to the amount of each substance present. Hence diphenylamine does not divert sterol intermediates into polyene synthesis, but causes a net increase in the formation of isoprenoid compounds. Exogenous β-carotene-C 14 was taken up by normal cultures but not by diphenylamine-treated mold. The distribution of lipids was unaffected by exogenous β-carotene in both normal and diphenylamine-treated cultures. The relation of these results to the mechanism of diphenylamine action is discussed.

Metabolic Activities of Sloughed Cells from the Jejunal Mucosa of Dogs with Thiry-Vella Loops.

Summary Three metabolic activities of sloughed epithelial cells of the dog jejunum were investigated. Sloughed epithelial cells as well as cells in the extrusion zone of the villus took up Nigrosin stain, while cells further down on the villus did not. Furthermore, sloughed cells did not incorporate acetate into non-saponinable lipid, whereas an equal number of cells in an intact intestinal slice did. Nonetheless, the particulate fraction of the succus entericus contained 95% of the total sucrase and alkaline phosphatase activity, and the sucrase activity was stable during incubation with the intestinal secretion. Based on this stability of sucrase and on the use of a simple flushing procedure, a dependable in vivo method of determining the sloughing rate is described.