The effect of alcohol on the in vitro absorption of estradiol and estrone sulphate in rat intestine

Cubilin is a 460-kDa multipurpose, multidomain receptor that contains an NH2-terminal 110-residue segment followed by 8 epidermal growth factor (EGF)-like repeats and a contiguous stretch (representing nearly 88% of its mass) of 27 CUB (initially found in complement components C1r/C1s, Uegf, and bone morphogenic protein-1) domains. Cubilin binds to intrinsic factor (IF)-cobalamin (cbl, vitamin B12) complex and promotes the ileal transport of cbl. The 460-kDa form of cubilin is the predominant form present in the apical brush-border membranes of rat intestine, kidney, and yolk sac, but a 230-kDa form of cubilin is also noted in the intestinal membranes. In thyroidectomized (TDX) rats, levels of intestinal brush-border IF-[57Co]-labeled cbl binding, 460-kDa cubilin protein levels and tissue (kidney) accumulation of cbl were reduced by ∼70%. Immunoblot analysis using cubilin antiserum of intestinal total membranes from TDX rats revealed cubilin fragments with molecular masses of 200 and 300 kDa. Both of these bands, along with the 230-kDa band detected in the total membranes of control rats and unlike the 460-kDa form, failed to react with antiserum to EGF. Mucosal membrane cubilin associated with megalin was reduced from ∼12% in control to ∼4% in TDX rats, and this decreased association was not due to altered megalin levels. Thyroxine treatment of TDX rats resulted in reversal of all of these effects, including an increase to nearly 24% of cubilin associated with megalin. In vitro, megalin binding to cubilin occurred with the NH2-terminal region that contained the EGF-like repeats and CUB domains 1 and 2 but not with a downstream region that contained CUB domains 2–10. These studies indicate that thyroxine deficiency in rats results in decreased uptake and tissue accumulation of cbl caused mainly by destabilization and deficit of cubilin in the intestinal brush border.

Download Full-text

Intestinal absorption of bile salts in the rat

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1964.207.1.1 ◽

1964 ◽

Vol 207 (1) ◽

pp. 1-7 ◽

Cited By ~ 86

Author(s):

Peter R. Holt

Keyword(s):

Normal Tissue ◽

Bile Salts ◽

Tissue Concentration ◽

Receptor Site ◽

Sodium Concentration ◽

Rat Intestine ◽

Tissue Water ◽

Active Absorption ◽

Common Receptor

Studies of taurocholate and cholate-C14 absorption by slices of rat intestine reveal that an active absorptive mechanism obeying Michaelis-Menten kinetics is present in the ileum but absent in other portions of the gut. Following 1 day of bile duct cannulation, the in vitro absorption of bile salts was enhanced two- to three-fold. The normal tissue concentration of bile salts in the ileum reached 1.3 µm and in the jejunum 0.35 µm/g tissue water. The presence of endogenous bile salts resulted in inhibition of subsequent ileal active absorption competitively suggesting the existence of a common receptor site for mucosal bile salt absorption. Active absorption was dependent on sodium concentration and inhibited by potassium. The significance of these results is discussed.

Download Full-text

Neurally maintained hypersecretion in undernourished rat intestine activated by E. coli STa enterotoxin and cyclic nucleotides in vitro.

The Journal of Physiology ◽

10.1113/jphysiol.1994.sp020285 ◽

1994 ◽

Vol 479 (1) ◽

pp. 159-169 ◽

Cited By ~ 6

Author(s):

H C Nzegwu ◽

R J Levin

Keyword(s):

Cyclic Nucleotides ◽

Rat Intestine ◽

E Coli

Download Full-text

Characterization in vitro of H+ secretion and H+:Na+ exchange by an organism normally inhabiting a CO2-rich environment: Hymenolepis diminuta (Cestoda) in the rat intestine

Canadian Journal of Zoology ◽

10.1139/z78-317 ◽

1978 ◽

Vol 56 (11) ◽

pp. 2344-2354 ◽

Cited By ~ 1

Author(s):

R. B. Podesta

Keyword(s):

Metabolic Pathways ◽

Intestinal Parasite ◽

Hymenolepis Diminuta ◽

Ambient Fluid ◽

Rat Intestine ◽

Ion Concentrations ◽

Intracellular Ion Concentrations ◽

Metabolic Reactions ◽

Stimulation Of

H+ and Na+ transport by the intestinal parasite Hymenolepis diminuta were studied in vitro. The flatworms acidified the ambient fluid by secreting H+ and the acidification could not be correlated with organic acid excretion. Ambient CO2-independent H+ secretion was attributed to protons of metabolic origin: dephosphorylation reactions and ionization of organic acids within the tissues. Ambient CO2-dependent H+ secretion was attributed to protons produced as a result of the hydration of CO2 within the tissue and to the stimulation of anaerobic metabolic pathways by CO2 acting as a cosubstrate in energy metabolism. Studies in which Na+ uptake was stimulated by CO2 or glucose and inhibited by ouabain, amiloride, or Na+ replacement suggested a partial direct coupling of Na+ absorption and H+ secretion but the different activation energies and the effect of buffer anions other than HCO3− suggested an indirect interaction. Various interactions were considered, including the effect of CO2 and intracellular ion concentrations on metabolic reactions leading to the supply of protons for H+ secretion and energy for ion transport.

Download Full-text

Some species differences in the intrinsic factor stimulation of B12 uptake by small intestine in vitro

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1959.197.4.926 ◽

1959 ◽

Vol 197 (4) ◽

pp. 926-928 ◽

Cited By ~ 21

Author(s):

T. Hastings Wilson ◽

Elliott W. Strauss

Keyword(s):

Small Intestine ◽

Guinea Pig ◽

Species Differences ◽

Intrinsic Factor ◽

Vitamin B ◽

Guinea Pig Ileum ◽

Rat Intestine ◽

Intrinsic Factors ◽

Stimulation Of

Sacs of everted small intestine from a variety of animals were incubated in bicarbonate-saline containing vitamin B12 with and without intrinsic factor (IF). B12 uptake by rat intestine was stimulated only by its own intrinsic factor. Guinea pig ileum responded to all intrinsic factors tested (guinea pig, rat, hog, hamster, human being and rabbit). The intestines of hamster and rabbit were intermediate in specificity, responding to some, but not all, of the IF preparations. Species differences occur in both the intestine and intrinsic factor preparations. The guinea pig ileum was suggested as a possible assay for both hog and human IF.

Download Full-text

NUCLEIC ACTD METABOLISM IN INTESTINAL MUCOSA: IV. THE EFFECT OF GLUCOSE ON INCORPORATION OF C14-FORMATE INTO PURINES AND PYRIMIDINES IN VITRO

Canadian Journal of Biochemistry and Physiology ◽

10.1139/y63-177 ◽

1963 ◽

Vol 41 (1) ◽

pp. 1557-1564

Author(s):

Beryl E. Stewart ◽

S. H. Zbarsky

Keyword(s):

Tumor Cells ◽

Ehrlich Ascites Tumor ◽

Ehrlich Ascites Tumor Cells ◽

Ascites Tumor ◽

Rat Intestine ◽

Maximal Stimulation ◽

Ehrlich Ascites ◽

Effect Of Glucose ◽

Rna And Dna

Slices of rat intestine were incubated in Krebs–Ringer phosphate buffer in the presence of C14-formate. The addition of glucose to the buffer stimulated the incorporation of radioactivity into the purines and, in some instances, the pyrimidines of the acid-soluble fraction and nucleic acids of the tissue. With Ehrlich ascites tumor cells studied under similar conditions, the increase in uptake of C14-formate into the purines was somewhat greater. The data suggest also that maximal stimulation with slices of intestine is obtained at glucose concentrations somewhat higher than that required with Ehrlich ascites tumor cells. A finding of interest was the increased incorporation of C14-formate into the thymine of the intestinal DNA in the presence of glucose. This result has not been observed with Ehrlich ascites tumor cells. Slices of rat intestine incubated for 2 hours in the presence of glucose had a higher content of RNA and DNA than tissue not exposed to added glucose.

Download Full-text