AJP - Gastrointestinal and Liver Physiology, Vol 250, Issue 2 177-G184, Copyright © 1986 by American Physiological Society
Postnatal maturation of enterocytes in sparse-fur mutant mice
C. Malo, I. A. Qureshi and J. Letarte
In adult sparse-fur mutant mice, ornithine transcarbamylase (OTC) activity
represents only 14% of the normal values. We studied the development of
this activity from birth to adult period and demonstrated that the enzyme
deficiency is already fully expressed at birth, in both the liver and the
small intestine of mutants. Since OTC catalyzes the conversion of ornithine
to citrulline, in the presence of carbamoyl-phosphate, the effect of a
disturbed ornithine metabolism on the postnatal development of the small
intestine has been evaluated. The normal appearance of sucrase as well as
the normal increase of glucoamylase, trehalase, and alkaline phosphatase
activities are delayed in sparse-fur mice compared with controls. Moreover,
normal adult values are never attained. In contrast, the normal decline of
lactase activity is impaired while leucylnaphthylamidase activity is
unaffected. Cell proliferation, as evaluated by [3H]thymidine incorporation
into DNA and mitotic index, is less active during the 3rd wk of life in
mutants. These phenomena are closely associated with a transient weak
arginase and ornithine decarboxylase activity in the small intestine. Since
arginase catalyzes the conversion of arginine to orthithine, thus ensuring
the availability of this substrate for ornithine decarboxylase activity,
these results indicate a disturbance of polyamine metabolism in mutant
enterocytes with a consequent delay in postnatal differentiation and
proliferation. Sparse-fur mutant mouse may therefore represent a useful
animal model for evaluating the role of ornithine metabolism in the
maturation process of the small intestine.
