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

Contraction and intracellular Ca²⁺ in ventricular myocytes from rats receiving fructose-enriched diets (FED) were investigated. Groups of mate Wistar rats received normal rat chow together with either normal drinking water or water containing 500 mM fructose ad libitum. Experiments were performed 12-14 weeks later. Rats receiving FED responded differently to a standard glucose tolerance test. Fasting blood glucose levels in FED and control rats were 48.5±2.3 (4) and 47.0±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 to controls (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 still significantly (p<0.01) higher than initial values. Amplitude and time to half (THALF) relaxation of ventricular myocyte shortening 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, diets supplemented with drinking water containing 500 mM fructose for a period of 12-14 weeks did not bave significant effects on ventricular myocyte shortening but did prolong the time course of the Ca²⁺ transient suggesting that defects in Ca²⁺ transport may precede defects in myocyte contractility in this experimental model.