AJP - Regulatory, Integrative and Comparative Physiology, Vol 256, Issue 3 612-R615, Copyright © 1989 by American Physiological Society
Effect of fasting on glucose turnover in a carnivorous fish (Hoplias sp)
C. R. Machado, M. A. Garofalo, J. E. Roselino, I. C. Kettelhut and R. H. Migliorini
Department of Morphology and Physiology, State University of Sao Paulo School of Veterinary Medicine, Brazil.
Intravenous glucose tolerance tests and measurements with [6-3H]glucose of
rate of glucose replacement, transit time, and body glucose mass were
performed in fed and fasted Hoplias malabaricus. Both glycemia levels and
the rate of decline of blood glucose following intravenous administration
of 500 mg/kg glucose were significantly lower in 60-day-fasted than in fed
fish. Changes in plasma free fatty acids were opposite to those in blood
glucose. The rate of glucose replacement, calculated graphically from mean
+/- 3 SE plots of glucose specific radioactivity, was 0.71 (0.66-0.77)
mg.kg-1.min-1 in fed H. malabaricus and decreased to 0.51 (0.46-0.56)
mg.kg-1.min-1 after 60 days without food, with a concomitant reduction of
body glucose mass (mmin, 138 vs. 83 mg/kg). In fish starved for 10 mo the
rate of glucose replacement and body glucose mass were further reduced to
0.35 (0.29-0.42) mg.kg-1.min-1 and 57 mg/kg (mmin), respectively. It is
concluded that a progressive decline in the rate of glucose utilization
contributes to the adaptation of fish to prolonged fasting.
