Comparison of glycogen store in rats and guinea-pigs: Effects of anaesthesia, fasting and re-feeding

Abstract

1. 1. Glycogen contents in the liver, muscle, heart and carcass were determined in rats (R) and guinea pigs (GP). The animals of the same initial body weight (400 g) were studied in five conditions: fed or normal (N) after 24 (F 24), 48 (F 48), 96 (F 96) hr of fast and after 24 hr of renutrition following 96 hr of fast (FR). 2. 2. Preliminary experiments were carried out to ascertain the experimental procedure. The less detrimental anaesthetic procedure was found to be ether in rats and nembutal in guinea pigs. 3. 3. In fed conditions, liver glycogen content was comparable in the two species (R = 73.7 ± 4.8; GP = 74.7 ± 11.5 mg.g −1) but hepatic store was larger in GP than in R (3584 ± 676 vs 2854 ± 231 mg.kg −1 BW) due to higher liver weight in GP than in R. Hepatic glycogen was totally exhausted in F 24 and remained low in F 48 and F 96. Hepatic glycogen was larger in FR than in control conditions (R:4000 ± 509; GP 3773 ± 663 mg.kg −1 BW). 4. 4. In fed conditions, the content of glycogen, in the anterior muscles of the thigh was 2.3 times higher in GP than in R (16.6 ± 0.9 vs 7.2 ± 1.2 mg.g −1). The utilization during fasting was more progressive and important in GP (F 24:10.3; F 24:8.9; F 96:6.8 mg.g −1) than in R (F 24:4.9; F 48:4.3; F 96:3.8 mg.g −1). In FR groups, muscular glycogen content was 28% higher than in control group in R but remained 29% lower than in control group in GP. 5. 5. In fed conditions, myocardial glycogen was 1.5 times higher in GP than in R (7.8 ± 1.2 vs 5.1 ± 0.6 mg.g −1). It was increased during fasting in R (F 24:6.7; F 48:7.4; F 96:8.7 mg.g −1) whereas it was decreased in FR conditions (4.1 mg.g −1). In GP after a decrease in F 24 (6.8 mg.g −1), myocardial glycogen was increased at F 48 (8.7 mg.g −1) and F 96 (10.1 mg.g −1) and was below control values in FR group (6.2 mg.g −1). 6. 6. In fed conditions carcass glycogen was higher in GP than in R (3287 ± 231 vs 2229 ± 288 mg.kg −1 BW). This parameter decreased during fasting in the two species (R: F24:1411; F 48:1035; F 96:798. GP: F 24:2283; F 48:1847; F96:1322 mg.kg −1 BW). In FR conditions, carcass glycogen was comparable to control conditions in R (2354 ± 180 mg.kg −1 BW) but remained low in GP (2520 ± 208 mg.kg −1 BW).