Thermal modulation of channel catfish intestinal dimensions, brush
border membrane fluidity, and glucose transport.
Houpe, Kristina L., Christiane Malo, Philip B. Oldham, and Randal K.
Buddington.
Department of Biological Sciences, Mississippi State University,
Mississippi State, MS 39762-5759, Department of Physiology,
University of Montreal, Montreal, Quebec, H3C 3J7, Canada, Department
of Chemistry, Mississippi State University, Mississippi State, MS
39762-5759
APStracts 3:0025R, 1996.
In light of the direct influence of temperature on metabolic rates and
dietary loads of ectotherms, intestinal responses were evaluated by
measuring 1) dimensions, 2) transapical initial rates of transport
using intact tissues and brush-border membrane vesicles (BBMV), and
3) BBMV fluidity using two size groups of channel catfish (Ictalurus
punctatus) acclimated to different water temperatures. Intestines of
larger fish at 15o C were 23% longer and 60% heavier than those at
30o C. Regardless of assay temperature, rates of glucose uptake by
fish held at 30o C relative to those at 15o C were two-fold higher
for intact tissues and over five-fold higher for BBMV. Although rates
of BBMV transport were higher for smaller fish, adaptive responses
were greater for larger fish. Temperature coefficients (Q10's) for
BBMV transport were higher between 5o and 15o C (3.5 to 4.5) relative
to 15o to 35o C (1.9 to 2.0), and may be partly related to the
inability of catfish held at low temperatures to adjust apical
membrane fluidity. Our findings indicate 1) cold acclimated catfish
maintain transport capacities by increasing intestinal dimensions, 2)
high acclimation temperatures increase rates of uptake by as yet
unknown mechanisms, 3) thermal modulation of transport varies among
species and nutrients, and 4) adaptive responses of ectotherms are
different from those of homeotherms.
Received 12 June 1995; accepted in final form 7 November 1995.
APS Manuscript Number R353-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 January 96