Testing of the assumptions made in estimating the extent of futile cycling

Journal Article · Mon May 01 00:00:00 EDT 1989 · Am. J. Physiol.; (United States)

OSTI ID:5904737

Wajngot, A; Chandramouli, V; Schumann, W C; Kumaran, K; Efendic, S; Landau, B R

In estimating glucose and fructose 6-phosphate futile cycling in vivo, complete detritiation of (2-/sup 3/H)glucose is assumed at the glucose 6-phosphate level, (3-/sup 3/H)glucose at triose phosphate formation, and (6-/sup 3/H)glucose in its conversion to glucose via pyruvate. (3-/sup 3/H)glucose detritiation via the pentose cycle is assumed to be negligible. Normal and non-insulin-dependent diabetic subjects, in the basal state and infused with glucose, were given (2-/sup 3/H,2-/sup 14/C)galactose, and /sup 3/H-to-/sup 14/C ratios in blood glucose were determined. (2-/sup 3/H,2-/sup 14/C)glucose was given with acetaminophen, and 3H/14C in urinary glucuronide was determined. Detritiation at glucose 6-phosphate was approximately 80%. (3-/sup 3/H,1-/sup 14/C)fructose was infused, and /sup 3/H//sup 14/C was determined in blood glucose and urinary glucuronide. At triose phosphate, 75-90% of the /sup 3/H was removed. The pentose cycle contribution was only a few percent. (6-/sup 3/H,6-/sup 14/C)glucose was infused, and 3H/14C in blood lactate was determined. (3-/sup 3/H,3-/sup 14/C)lactate was infused, and ratios in blood glucose were determined. Maximally, 10% of /sup 3/H from (6-/sup 3/H)glucose was retained. If glucose and galactose are metabolized in the same hepatic site(s), glucose conversion to three-carbon intermediates in the indirect pathway of glycogen formation occurs in extrahepatic tissue(s). Reported estimates of futile cycling, although qualitatively correct, quantitatively require correction.

• Research Organization: Karolinska Hospital, Stockholm (Sweden)
• OSTI ID: 5904737
• Journal Information: Am. J. Physiol.; (United States), Vol. 256
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CARBON 14
ISOTOPE RATIO
GALACTOSE
METABOLISM
GLUCOSE
TRITIUM
BLOOD
CARBON 14 COMPOUNDS
DIABETES MELLITUS
GLYCOGEN
LIVER
MAN
TRACER TECHNIQUES
TRITIUM COMPOUNDS
ALDEHYDES
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOLOGICAL MATERIALS
BODY
BODY FLUIDS
CARBOHYDRATES
CARBON ISOTOPES
DIGESTIVE SYSTEM
DISEASES
ENDOCRINE DISEASES
EVEN-EVEN NUCLEI
GLANDS
HEXOSES
HYDROGEN ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
LIGHT NUCLEI
MAMMALS
MATERIALS
METABOLIC DISEASES
MONOSACCHARIDES
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANS
POLYSACCHARIDES
PRIMATES
RADIOISOTOPES
SACCHARIDES
VERTEBRATES
YEARS LIVING RADIOISOTOPES
550501* - Metabolism- Tracer Techniques