ELECTROCARDIOGRAPHIC CHANGES IN DIABETES MELLITUS IN RATS

The European College of Veterinary Internal Medicine  – Companion Animals.

17 ^th ECVIM-CA Congress & 9 ^th ESVCP Congress.

13 ^th – 15 ^th September 2007 – Budapest – Hungary.

p. 228.

Electrocardiographic changes made by diabetes mellitus experimentaly induced in WhitE  wistar rats

Brăslaşu Corneliu Mihail¹, Brăslaşu E. Daniela ¹, Brădăţan Cătălina¹,

Săvulescu Ilinca Mihaela², Cojmăleaţă Roxana², Budai Mihai¹.

¹Faculty of Veterinary Medicine Bucharest,

²University of  Medicine and Pharmacy „Carol Davila” Bucharest, Romania.

Diabetes  mellitus is a complex metabolic disorder who can affect disorders at coronary artery and determine a specific cardiomyopathy.

Two lots were made, first – the lot with streptozocin administration (60 mg/kg - 50 Mm citrate buffer)  and the second lot – standard lot.

Diabetics animals (n.38) presented an acute course (15 animals) or a chronic course (23 rats). In the first situation, the rats had died in the first 10 days since diabetes mellitus has been induced and the animals presented: inappetency, emaciation, deep deviation – hyperglycemic coma, haematuria ( one case) and  bloody diarrhea (one case). Blood glucose value was  600mg/dl.

The rats with a chronic course initially presented inappetence, then they started to feed themselves and the body weight started to be almost the same with the standard lot weight. Blood glucose value was 406,22+24,85 mg/dl.

The rats with a acute course presented electrocardiographic  changes: bradycardia, left bundle branch block, ST segment depression, atrial standstill, first, second and third degree AV block and ventricular fibrillation.

In  diabetics rats with a chronic course the electrocardiographic diagnosis was: left ventricular enlargement, right ventricular enlargement and ST segment depression. In conclusion, we think that in rats with acute course the ECG’s changes followed diabetic cetoacidosis (blood exams confirmed), but in rats with chronic course the changes were induced by cardiac and coronary artery changes (histologic confirmed).

Material and Method

45 adult Wistar male rats, weighing 200-220gr were used in the experiment.

They were divided in 2 groups:

-         the control group (n=7)

-         the group with induced diabetes melitus by streptozocine administration (n=38)

Diabetes melitus was induced by one administration of streptozocine, intraperitoneally, in a dose of 60mg/kg in 50 Mm buffer citrate.

A clinical and paraclinical diagnosis – determination of blood sugar with the Accu-Check Go (Roche) glucometer - of diabetes mellitus was realized.

The blood samples were taken from the coccygeal arteries.

The electrocardiograms were realized on awake and right lateral decubitus animals (manual setting of the animals).

The ECG parameters were: standard leads; amplitude=1Mv=10mm; 25 and 50mm/sec.

Animal  breeding, examination and  euthanasia were realized according to the Romanian legislation of animal protection.

The time-points for the sacrifice were at 14, 30 and 60 days. The euthanasia was realized after animals anesthesia. Samples from heart, aorta, pancreas and liver were collected for the histological exam.

Results and debates

The diabetes melitus was diagnosed in 38 Wistar white rats after the administration of streptozocine, which means 60% of the animals receiving a streptozocine administration.

15 rats developed the acute form of Diabetes melitus and 23 the chronic form of Diabetes.

Clinical diagnosis

The clinical syptoms in the acute form of diabetes  were represented by anorexia, cahexia, deep depression – hyperglicemic coma, haematuria (1 case) and bloody diarrhea ( 1 case). The rats died in the first 10 days from the administration of streptozocine. The glycemia level was over 406,22+/-24,85mg/ml.

In the first stages of the chronic form, the symptoms were represented by anorexia and weakness. Afterwards, the animals begin to eat their meal and the body weigh became comparable with the control group. The animals were more weakened comparing to the control group which allowed multiple blood samples and EKG exams in very good conditions.

The glycemia level was 406,22+/-24,85mg/dl.

           

Electrocardiographic diagnosis

The electrocardiograms were realised in awake, right lateral decubitus animals by manual setting.

In the acute form, EKG changes were represented by: bradycadia, left bundle branch block, ST segment depression, nodal rhythm, first, second and third AV block and ventricular fibrillation (as terminal arithmia).

In the chronic form, EKG changes were left ventricular hypertrophy, right ventricular hypertrophy and ST segment depression.

            We consider that these changes are due:

1. in the acute form, to the diabetic ketoacidosis;
2. in the chronic form, to the changes of the cardiac musculature

Left bundle branch block, Synusal  bradycardia – 130 beats/min.

Ventricular fibrillation – terminal phase

Second – degree AV block. Mobitz II.

ST segment supradenivelation

Sinusal bradycardia with SA block

 Sinusal bradycardia

Intense sinusal bradycardia – right bundle branch block

Same case

ST segment depression

Left ventricular enlargement

ECG initial aspect of above case

The histolological lesions revealed:

-         strong vasodilatation, dystrophy and necrosis – in the case of rats with a fast evolution

-         vasodilatation and fibrosis in atrium and myocardium, particularly in the papilar muscles and interventricular septum.

 Myocardium. Arteriole and venule blocked by hematic thromb

Degenerative and necrotic areas due to the partial obstruction (+85%)

 of arteriole lumen – mixt thrombus.

Partial thrombosis of an arteriole lumen. The adhesion

of the thrombus on the vascular endothelium can be observed.

Intense fixation area of myofibrilla postinfarct

Distrophia and microfocus of miofibrilar necrosis

Section through the aorta.

Distrophic and micronecrotic lesions of endothelial areas and

calcium sedimentation at the vascular intima level can be observed.

CONCLUSIONS

1.      Diabetes mellitus was induced by streptozocine administration (60mg/kg) intraperitoneally, in an unique dose. From the total number of male rats, only 60% (38 rats) has developped diabetes mellitus. 15 rats (39,47%) have had a fast evolution and 23 (60,52%) a chronic form.

2.      The clinical signs in the acute form were: anorexia, fast and advanced weakening, deep depression (hyperglicemic coma), hematuria, bloody diarrhea and death in the first 10 days from the administration of streptozocin. The level of glycemia was 600 mg/dl.

3.      The symptoms of the chronic form were initial anorexia and decreased liveliness. The level of glycemia was 406,22+/-24,85mg/dl.

4.      The EKG changes in the acute form were represented by: bradycardia, left bundle branch block, ST segment depression, nodal rhythm, first, second and third AV block and ventricular fibrillation (as terminal arithmia). These changes are the consequence of the diabetic ketoacidosis.

5.      In the chronic form, EKG changes were: left ventricular hypertrophy,   right ventricular hypertrophy and ST segment depression, which demonstrates myocardial changes, as a consequence of long term hyperglycemia.

6.      Histologic changes were represented by strong vasodilatation, dystrophy and necrosis – in the case of rats with a fast evolution and vasodilatation and fibrosis in atrium and myocardium, particularly in the papilar muscles and interventricular septum.

7.      The injuries observed in these experimental studies are similar with the lesions of human patients (and also in dog), which represents a strong reason to continue the research and to transpose the results in the field of dog’s cardiology.

REFERENCES

1. Brăslaşu C.M., Ciobotaru Emilia, Militaru Manuela, Şonea Al., Brăslaşu Elena Daniela, Dinescu Georgeta, Diaconescu Al., Soare Teodoru, Stănciulescu Cornelia, 2005 - Corelaţia dintre disfuncţia endotelială şi afectarea miocardică la pacienţii cu diabet zaharat. Contract cercetare CEEX, 55/2005. Contract VIASAN. Director de contract. Prof. I. Bruckner.
2. Cheţa D., 2002 – New insights into experimental diabetes. Editura Academiei Române, Bucureşti.
3. Ding Y., Zou R., Judd R.L., Zhong J., 2006 – Effects of gender difference on cardiac myocite dysfunction in streptozocin - induced diabetic rats. Endocrine, 29, 1, 135 – 141.
4. Kloting I., Vogt L., 1993 – Influence of sex and phenotype of parents on the incidence of diabetes in BB/OK rat litters. Diabete Metab., 19, (1 Pt 2), 178 – 182.
5. Kohn D.F., Clifford C.B., 2002 – Biology and diseases of rats. In: J.G. Fox, L.C. Anderson, F.M. Lowe et al., eds. Laboratory Animal Medicine, 2^nd ed. New York Academic Press, 121 – 167.
6. Nogueira F.N., Santos M.F., Nicolau J., 2005 – Influence of streptozocin – induced diabetes on hexokinase activity of rat salivary glands. J. Physiol. Biochem., 61, 3, 421 – 427.