Title

An investigation of frequency and length changes in diabetic papillary muscles.

Date of Award

1993

Degree Type

Thesis

Degree Name

M.H.K.

Department

Kinesiology

First Advisor

Kenno, K.

Keywords

Biology, Animal Physiology.

Rights

CC BY-NC-ND 4.0

Abstract

The length-dependence of several excitation-contraction coupling elements were investigated in diabetic papillary muscles. Female Wistar rats (200-300 g) were chemically-induced with a single tail vein injection of streptozotocin (65 mg/kg) and sacrificed a minimum of 5 weeks later. Twitch curves at 100 and 95%L$\sb{\rm max}$ (percentage of optimal length) of diabetic myocardium, compared to the control group, demonstrated significant, p $<$ 0.05, depressions in the maximal rates of contraction and relaxation, and prolongation of the time to peak contraction, the time to maximal relaxation, time to the maximal rate of contraction and relaxation. The reduction of muscle length caused similar significant, p $<$ 0.05, depressions of these parameters including peak muscle force, in both the control and diabetic groups, although in the diabetic group there was no significant change in the maximal rate of relaxation. Force-interval data revealed that diabetes caused significant depressions, p $<$ 0.05, of both the beta and gamma phases at 100 and 95%L$\sb{\rm max}$ The reduction of muscle length caused significantly greater, p $<$ 0.05, potentiation during the beta and gamma phases at 95%L$\sb{\rm max}$ in the control group, however, there were no significant differences observed in the diabetic group. The addition of ryanodine (1 $\mu$M) coupled with increases in frequency, 1.67, 2.50, 3.33 and 5.00 Hz, was used to investigate whether diabetes caused an alteration of the calcium influx through the slow calcium channel. Both the control and diabetic groups exhibited negative inotropic effects, and upon an increase in stimulation from a pacing frequency of 0.5 Hz, produced positive staircases. Comparison was accomplished by assessing the number of beats required to attain relative percentages of the staircase force. There were no significant differences, p $<$ 0.05, at 100 and 95%L$\sb{\rm max}$ between the control and diabetic groups although it seemed that fewer beats were required for the diabetic group to achieve relative percentages of staircase force. Upon a reduction in muscle length, both the control and diabetic groups exhibited, in almost every comparison, no significant differences, p $<$ 0.05, in the number of beats required to reach a relative percentage of staircase force.Dept. of Kinesiology. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1993 .A576. Source: Masters Abstracts International, Volume: 32-06, page: 1598. Adviser: Kenji Kenno. Thesis (M.H.K.)--University of Windsor (Canada), 1993.