Comparison between spontaneously beating atria from control and streptozocin-diabetic rats

Abstract

Isolated spontaneously beating atria from streptozocin diabetic rats were compared with those from controls. Diabetic atria were found to have reduced rates, increased forces of contraction and reduced sensitivity to the inotropic effects of noradrenaline, isoprenaline, tyramine and calcium. Positive chronotropic responses to tyramine were also reduced but those to noradrenaline and isoprenaline were increased suggesting that tyramine releasable stores of noradrenaline were reduced. Elevation of glucose concentration in the medium from 5·6 to 27 min resulted in a decrease of inotropic sensitivity to the agents used in both control and diabetic rat atria. Resting contractile force of control rat atria was reduced by the inclusion of either 22 niM 2‐deoxyglucose, 10−3 i.u. insulin ml−1 or 5 mM acetate in the medium. The rate was also reduced by medium containing 2‐deoxyglucose but increased by insulin. 2‐Deoxyglucose also reduced inotropic but increased chronotropic sensitivity to isoprenaline. Possible mechanisms responsible for the changes observed are discussed.

Characteristics of Autonomic Nervous Function in Zucker-Fatty Rats: Investigation by Power Spectral Analysis of Heart Rate Variability.

“…These results agree with earlier reports using telemetric monitoring in Zucker-fatty rats [2,3,19]. This tendency was also observed in WBN/Kob diabetic rats and streptozotocin-diabetic rats [11,13]. Although autonomic neuropathy is a well-documented complication in diabetic patients, Van Buren et al [25] reported that the reduced HR in diabetic rats is not derived from autonomic nervous dysfunction.…”

Effects of bata-adrenoceptor blocking agents on isolated atrial and papillary muscles from experimentally diabetic rats.

“…This lower R in the atrium coincided with other results that the basal value of R in the right atrium decreased in the isolated myocardium of ex perimentally diabetic animals (7,9,18,22). On the other hand, in contrast to the present result, Fein et al (19) reported that the basal value of -dF/dt decreased more markedly than that of +dF/dt in the left ventricular papillary muscle of diabetic rats.…”

Blood glucose and atherosclerosis.

“…The hearts of streptozotocin diabetic rats were shown to have abnormalities in left ventricular contraction and relaxation, 33 in relaxation of isolated papillary muscle, 34 and in the contraction and response to catecholamines of isolated atria. 35 Alloxan diabetic dogs were shown to have impaired cardiac function and an accumulation of cholesterol and triglyceride in the myocardium. 36 Evidence for decreased response to stress in the diabetic heart has come from studies of the effect of increasing ischemia on the development of cardiac failure in alloxan diabetic rats.…”