Contraction and intracellular Ca2+ in ventricular myocytes from rats receiving fructose-enriched diets

Abstract

Contraction and intracellular Ca²⁺ in ventricular myocytes from rats receiving fructose-enriched diets (FED) wereinvestigated. Groups of male Wistar rats received normal rat chow together with either normal drinking water or watercontaining 500 mM fructose ad libitum. Experiments were performed 12-14 weeks later. Rats receiving FED respondeddifferently to a standard glucose tolerance test. Fasting blood glucose levels in FED and control rats were 48.5±2.3 (4) and47.0±1.9 (4) mg/dl, respectively. At 30 min after intraperitoneal administration of glucose (2g/kg body weight),concentrations of blood glucose were significantly (p<0.05) higher in rats receiving FED (206.3±19.5 mg/dl) compared tocontrols (150.3±8.5 mg/dl). At 120 min, blood glucose in FED (87.3±4.2) and control (80.3±3.4 mg/dl) rats were stillsignificantly (p<0.01) higher than initial values. Amplitude and time to half (THALF) relaxation of ventricular myocyteshortening and Ca2+ transient were not altered by FED. Time to peak (TPK) shortening was unaltered, however, the TPK Ca²⁺transient was significantly prolonged in FED rats (65.1±3.4 ms) compared to controls (56.4±2.0 ms). In conclusion, dietssupplemented with drinking water containing 500 mM fructose for a period of 12-14 weeks did not have significant effects onventricular myocyte shortening but did prolong the time course of the Ca2+ transient suggesting that defects in Ca²⁺ transportmay precede defects in myocyte contractility in this experimental model.