1. An account is given of the absorption of @entity7967 by the small intestine of Rana temporaria, R. pipiens and Bufo vulgaris perfused in vitro through the vascular system. Maltase and @entity69986 activity are found in the intestine of all three species; very small amounts of sucrase are present in the intestine of R. pipiens but there is no evidence for the presence of @entity290 in any of the animals studied.2. During @entity7969 absorption free @entity413 appears in the vascular effluent and in the intestinal lumen. Only very small quantities of @entity7016 are found in the vascular effluent. The concentration of free @entity413 in the intestinal lumen during @entity7969 absorption is not high enough to account for the rates of @entity413 transport observed. The rate of appearance of @entity413 in the vascular effluent is determined by the concentration of @entity7016 in the luminal fluid, and @entity12015 , free in solution in the lumen, is not an obligatory intermediate in the process of @entity7016 absorption.3. For R. pipiens more than 90% of the maltase activity in the system is present in the intestinal wall and the rate of @entity7969 hydrolysis by maltase, free in the intestinal lumen, is found to be inadequate to account for the rates of appearance of @entity413 observed to occur in the lumen and in the vascular effluent. It is not possible to wash away maltase activity from the intestinal wall.4. The kinetic properties of maltase and @entity69986 acting in situ are of the Michaelis-Menten type; the apparent K(m) is 2 mM for maltase, and 3 mM for @entity69986 .5. The relationship which exists between the rate of absorption of @entity413 and the concentration in the luminal fluid of either @entity7016 or free @entity413 is of the Michaelis-Menten type. Expressed in molar units, the apparent K(m) for the @entity413 transport is about one fifth that of the disaccharidase. The maximum rate of @entity413 transport observed is less than the maximum rate of @entity7016 hydrolysis. In R. pipiens equimolar concentrations in the intestinal lumen of the monomer free @entity413 , or of the dimer, @entity7969 , yield approximately equal rates of transport of the free @entity12015 .6. It is concluded that in the amphibian, either intestine @entity7016 hydrolysis and @entity413 transport are functions of separate subcellular systems which spatially are very closely related, or that the hydrolysis and transport are different facets of the activity of a common system.

XXXX absorption by amphibian small intestine in vitro.

@entity7967 :: ('MESH:D004187', 'Chemical') :: ['disaccharides'] @entity290 :: ('3938', 'Gene') :: ['lactase'] @entity7969 :: ('MESH:D008320', 'Chemical') :: ['maltose'] @entity69986 :: ('11181', 'Gene') :: ['trehalase'] @entity12015 :: ('CHEBI:18133', 'Chemical') :: ['hexose'] @entity7016 :: ('CHEBI:36233', 'Chemical') :: ['disaccharide'] @entity413 :: ('MESH:D005947', 'Chemical') :: ['glucose']
@entity7016 :: (CHEBI:36233,Chemical) :: ['Disaccharide']
