Sucrose feeding effects inhibition of gamma-glutamyltranspeptidase in the liver of the rat: possible mediation by thyroid hormone.
The effect of sucrose on Fischer 344 rat liver gamma-glutamyltranspeptidase (gammaGT) was studied: in adults fed sucrose for 3 weeks; and rats exposed to sucrose from the 18th day of gestation to the 40th day after birth. Rats fed regular rodent chow served as controls. Sucrose caused mild lipemia; and in the liver an increase in size and fat build-up without damage. In adult sucrose-fed rats, compared to controls, plasma glucose levels were increased: 1.12-, 1.40- and 1.13-fold after 24, 48h and 3 week consumption of sucrose, respectively. Insulin levels were unaltered for the first week of sucrose consumption but increased from control levels: 16% at 1 week, and 2.0-fold at 3 weeks. The T3 levels were comparable to control levels 24h after the sucrose was started and were increased: 1.22-, 1.13- and 1.12-fold at 48h, 1 and 3 weeks, respectively. The T4 levels were comparable at all time points between sucrose-fed and control rats. Liver gammaGT activity exhibited a steady decrease from control levels: after 24, 48h, 1 and 3 weeks of sucrose feeding the decrease was 5, 8, 21 and 37%, respectively in homogenates; and 10, 17, 24 and 41%, respectively in plasma membranes. Perinatal sucrose exposure effected in 40-day-old rats, compared controls: a 1.09-fold increase in plasma glucose; no change in plasma insulin; an increase of 1.15- and 1.39-fold in plasma levels of total and free T3, respectively; a decrease of 20 and 14% in plasma levels of total and free T4, respectively. gammaGT activity was decreased in liver plasma membranes isolated from sucrose-exposed rats relative to those of control: 80% in the male; 82% in the female. Relative specific activities of gammaGT were the same in both males: 15.4 and 16.1 in control and sucrose-exposed male rats, respectively; and females: 14.1 and 15.4 in control and sucrose-exposed female rats, respectively. gammaGT was 2-fold higher in the livers of female relative to male rats in sucrose-exposed and control groups. Kidney gammaGT activities were the same in control and sucrose-exposed rats. The involvement of T3 in the sucrose-induced decrease in liver gammaGT is discussed.
Hemmings
Susan J
SJ
Department of Physiology, College of Medicine, University of Saskatchewan, 107 Wiggins Road, Saskatoon, Saskatchewan, Canada S7N 5E5. hemmings@sask.usask.ca
Takaya
Satchan
S
D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D001786:Blood Glucose / Q000032:analysis; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004032:Diet; D005260:Female; D007328:Insulin / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D011247:Pregnancy; D011863:Radioimmunoassay; D051381:Rats; D011916:Rats, Inbred F344; D012737:Sex Factors; D013395:Sucrose / Q000494:pharmacology*; D013963:Thyroid Hormones / Q000378:metabolism*; D005723:gamma-Glutamyltransferase / Q000037:antagonists & inhibitors* / Q000378:metabolism
D001786:Blood Glucose; D007328:Insulin; D013963:Thyroid Hormones; D013395:Sucrose; D005723:gamma-Glutamyltransferase