AJP - Regulatory, Integrative and Comparative Physiology, Vol 240, Issue 3 246-R252, Copyright © 1981 by American Physiological Society
Amino acid gluconeogenesis and glucose turnover in kelp bass (Paralabrax sp.)
K. Bever, M. Chenoweth and A. Dunn
The glucose replacement rate, plasma glucose concentration, glucose body
mass, and amino acid gluconeogenesis were determined in vivo in fed and
fasted kelp bass (Paralabrax clathratus) using [6-3H]glucose administered
with [U-14C]glutamate, [U-14C]aspartate, or [U-14C]alanine. Fasting (14
days) and prolonged starvation (72 days) do not produce changes in the
replacement rate, body mass, or plasma concentration of glucose. The
removal of amino acids from the circulation is rapid in both fed and
fasting states with nearly 50% of the administered 14Ctracer disappearing
by 5 min. The incorporation of [14C]amino acid carbon into the body glucose
mass is also rapid with significant amounts of tracer appearing within 15
min after administration. Gluconeogenesis from alanine and glutamate is
increased by fasting whereas that from aspartate is diminished. The
gluconeogenic rate is comparable to that previously observed in rats (Dunn,
A., M. Chenoweth, and J. G. Hemington. The relationship of adrenal
glucocorticoids to transaminase activity and gluconeogenesis in the intact
rat. Biochim. Biophys. Acta 237: 192-202, 1971), although the glucose
replacement rate is significantly lower. We propose that the paradoxically
high rate of gluconeogenesis in fish may serve to provide carbohydrate
precursors for mucus synthesis in these carnivorous animals with limited
carbohydrate intake.
