title: Alterations in alpha 1-adrenoceptor stimulation of isolated atria from experimental diabetic rats.
abstract: This purpose of this investigation was to determine the influence of experimental diabetes (3 months) on the responsiveness of rat isolated atria to alpha 1-adrenoceptor stimulation by phenylephrine. Diabetes was chemically induced with streptozotocin (65 mg/kg i.v.) in 42- to 43-day-old, nonfasted male Sprague-Dawley derived rats. Chronotropic (right atria) and inotropic (left atria) indices were recorded in response to alpha 1-adrenoceptor stimulation by phenylephrine. These experiments were performed in the presence of beta-adrenoceptor antagonism (timolol). Isolated right atria from diabetic rats demonstrated a greater increase in heart rate in response to phenylephrine than did corresponding control atria. Left atria were supersensitive (decrease in EC50 values) and hyperresponsive to alpha 1-adrenoceptor stimulation by phenylephrine when compared with stimulation of control left atria. Diabetic left atria in response to phenylephrine were observed to exchange more radioactive calcium (45Ca2+) than control left atria, whereas both diabetic and control left atria exchanged the same amount of 45Ca2+ during basal contractile conditions. Phenylephrine had no effect on 45Ca2+ efflux from either diabetic or control atria. These results indicate that 3 months of uncontrolled experimental diabetes in the rat produces an enhancement of alpha 1-adrenoceptor activation of isolated atria, and that there is an alteration in Ca2+ mobilization which may contribute to the enhanced receptor activation.
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D002118:Calcium / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D006321:Heart / Q000503:physiopathology*; D006325:Heart Atria / Q000187:drug effects / Q000503:physiopathology; D066298:In Vitro Techniques; D007328:Insulin / Q000097:blood; D007700:Kinetics; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism; D010656:Phenylephrine / Q000494:pharmacology*; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D013999:Timolol / Q000494:pharmacology
chemical_list: D001786:Blood Glucose; D007328:Insulin; D011942:Receptors, Adrenergic, alpha; D010656:Phenylephrine; D013999:Timolol; D002118:Calcium; D011224:Prazosin