AJP - Gastrointestinal and Liver Physiology, Vol 258, Issue 5 770-G773, Copyright © 1990 by American Physiological Society

ARTICLES

Ontogenetic development of transporter regulation in bullfrog intestine

E. M. Toloza and J. M. Diamond
Department of Physiology, University of California Medical School, Los Angeles 90024-1751.

Intestinal nutrient transporter activity is adapted to dietary substrate levels on three time scales: reversibly, within an adult individual, to rapid dietary changes; developmentally, to normal ontogenetic changes in diet; and evolutionarily, among carnivores, omnivores, and herbivores, to a species' natural diet. Does the capacity for rapid reversible adaptation itself vary adaptively during development? Substrate-dependent regulation would make functional sense in herbivorous/omnivorous tadpoles in which dietary substrate levels fluctuate unpredictably, but would serve no purpose in strictly carnivorous adult bullfrogs in which dietary protein is always high and carbohydrate is low. Hence, we fed premetamorphosis bullfrog tadpoles either boiled lettuce (high in carbohydrate, low in protein) or ground beef (high in protein, low in carbohydrate). Gut weight relative to body weight was higher in lettuce-fed tadpoles. Glucose uptake was greater and proline uptake slightly less in lettuce-fed than in beef-fed tadpoles. The resultant ratio of glucose uptake capacity to proline uptake capacity was nearly twice as high in lettuce-fed as in beef-fed tadpoles, corresponding to a much higher ratio of dietary carbohydrate to protein. Adult frogs have been shown to lack such regulation. Therefore, the regulatory capacity seen in tadpoles must become lost during amphibian metamorphosis.

This article has been cited by other articles:

				L. Jiang, E. S. David, N. Espina, and R. P. Ferraris GLUT-5 expression in neonatal rats: crypt-villus location and age-dependent regulation Am J Physiol Gastrointest Liver Physiol, September 1, 2001; 281(3): G666 - G674. [Abstract] [Full Text] [PDF]

				R. Shu, E. S. David, and R. P. Ferraris Luminal fructose modulates fructose transport and GLUT-5 expression in small intestine of weaning rats Am J Physiol Gastrointest Liver Physiol, February 1, 1998; 274(2): G232 - G239. [Abstract] [Full Text] [PDF]