Contraction and intracellular free ca2+ concentrations in ventricular myocytes from rats recieving sucrose-enriched diet

ABSTRACT

Contraction and intracellular free Ca2+ concentrations [Ca2+]i in ventricular myocytes from rats receiving sucrose-enriched diets [SED's] were investigated. Groups of Wistar rats received normal rat chow together with either normal drinking water or water containing 500 mM sucrose ad libitum. Experiments were performed 12-14 weeks later. Rats receiving SED's responded differently to a st and ard glucose tolerance test. Fasting blood glucose levels in SED and control rats were 59.4 +/- 1.3 and 58.8 +/- 1.4 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 SED [256.2 +/- 32.7 mg/dl] compared to controls [136.6 +/- 14.7 mg/dl]. At 120 min blood glucose in SED [67.6 +/- 7.2] and control [63.0 +/- 2.4 mg/dl] rats were not significantly [P>0.05] different when compared to initial fasting blood glucose values. Blood plasma insulin concentrations in SED and control rats were 3.01 +/- 0.55 [5] and 0.29 +/- 0.05 [5] ng/ml, respectively. Amplitude and time to peak [TPK] of ventricular myocyte shortening and Ca@@@@@@ transient were not altered by SED. Time to half [THALF] relaxation of shortening was significantly prolonged in myocytes from SED [60.6 +/- 2.1 ms] compared to control [48.7 +/- 2.9 ms] rats. The TPK and THALF relaxation of the Ca2+ transient were not altered by SED. However, the amplitude of Ca2+ transient was significantly increased in myocytes from SED [0.36'0.02 RU] compared to control [0.31 '0.02 RU] rats. Altered myofilament sensitivity to Ca2+ may underlie the contractile defects seen in ventricular myocytes from rats fed diets that are supplemented with drinking water containing 500 mM sucrose for 12-14 weeks