Chronotropic function in spontaneously diabetic BB rats.
In the present study, isolated atrial function in spontaneously diabetic BB Wistar rats maintained for 12 weeks on a low (BB-LI) and a high (BB-HI) dosage of insulin was examined. Basal atrial rates were unchanged in the diabetic animals, relative to nondiabetic littermates (ND-BB) or Wistar controls. The BB-HI animals were euglycemic and responded to isoproterenol in a similar manner to the ND-BB and Wistar control animals. In contrast, BB-LI animals remained hyperglycemic and exhibited lower responses to the maximum chronotropic effects of isoproterenol. Plasma thyroid hormone levels were unaltered in the BB-diabetic animals. These results therefore reveal an absence of bradycardia and hypothyroidism in spontaneously diabetic BB rats, in contrast to previous observations in streptozotocin diabetic rats. However, a decrease in chronotropic response to isoproterenol was still noted in the BB-LI animals. These findings suggest that decreased positive chronotropic effect of isoproterenol in diabetes may not be a direct consequence of altered thyroid status.
Division of Pharmacology, Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, Canada.
S
S
Ramanadham
G M
GM
McGrath
J H
JH
McNeill
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight; D003921:Diabetes Mellitus, Experimental / Q000235:genetics / Q000503:physiopathology*; D006339:Heart Rate; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009206:Myocardium / Q000378:metabolism; D051381:Rats; D011913:Rats, Inbred BB; D011919:Rats, Inbred Strains
D001786:Blood Glucose; D007545:Isoproterenol