Prothrombotic effects of short-term aldosterone infusion
in adrenalectomized diabetic rats

P Szoka1, A Zakrzeska1, J Szemraj2, W Kisiel1, E Chabielska1. 1Medical University of Bialystok, Department of Biopharmacy, 15-222, Poland, 2Medical University of Lodz, Department of Medical Biochemistry, 92-215, Poland

Introduction: Diabetes is associated with numerous hematologic and rheologic abnormalities that might predispose to thrombosis and lead to an increased risk of cardiac events. There are data indicating that aldosterone (ALDO) may be one of the factors responsible for activation of the coagulation cascade and impairment of fibrynolysis in diabetes. In recent years, the role of rapid nongenomic actions of aldosterone on cardiovascular events have received particular attention. There is now a growing evidence that nongenomic actions of ALDO are mediated via some classical mineralocorticoid receptors (MR) as well as glicocorticoid receptors (GR). We previously demonstrated that short-term ALDO infusion enhances experimental venous thrombosis in normoglicemic rats (Thromb Haemost 2007, JRAAS 2011).

The aim of the present study was to investigate in adrenalectomized diabetic rats

1. the effect of ALDO on arterial thrombus formation
2. the role of MR and GR in ALDO prothrombotic action.

Materials and methods: Bilateral adrenalectomy (ADX) was performed in Wistar rats (300-350g; n=7-12) to eliminate the impact of endogenous adrenal hormones. After two weeks diabetes was induced with single injection of streptozotocin (STZ; 65 mg/kg; i.p.). Arterial thrombosis was induced by electrical stimulation of the common carotid artery. Carotid blood flow was monitored continuously using a Doppler flow probe (1 mm-diameter, Hugo Sachs Elektronik – Harvard Apparatus GmbH, Germany). Aldosterone (ADX+STZ+ALDO, 30 μg/kg/h) or vehiculum (ADX+STZ+VEH, 0.4% ethanol; 2 ml/kg/h) were infused into the femoral vein 5 minutes before arterial thrombosis induction and was continued for 1 hour. Eplerenone, a selective MR antagonist (ADX+STZ+EPL+ALDO, 100 mg/kg; p.o.) or RU-486, GR antagonist (ADX+STZ+RU-486+ALDO, 10 mg/kg; s.c.), were administered 30 minutes before ALDO infusion. Initial blood flow (IBF), final blood flow (FBF), time to total occlusion and thrombus weight were assessed. Plasma aldosterone level was measured by radioimmunoassay.

Results: Plasma ALDO level was undetectable in adrenalectomized rats. After ALDO infusion hormone level in plasma was 1950±24 pg/ml and significantly increased to 4192±88 pg/ml (p<0,01) after EPL administration. The IBF and incidences of total occlusion were comparable in all groups. The FBF in the ADX+STZ+ALDO group was decreased as compared with ADX+STZ+VEH (3,4±1,4 ml/min vs 6,0±1,6 ml/min). There was tendency to increase in FBF after EPL (4,4±1,0 ml/min) or RU-486 (4,6±0,7 ml/min) administration as compared with ADX+STZ+ALDO group (3,4±1,4 ml/min). Marked increase in thrombus weight was observed after acute ALDO infusion (1,2±0,1 mg vs 0,5±0,1 mg in ADX+STZ+VEH group; p<0,01). Administration of EPL (0,4±0,1 mg) or RU-486 (0,4±0,1 mg) significantly reduced thrombus weight as compared with ADX+STZ+ALDO group (1,2±0,1 mg; p<0,001; p<0,001).

In conclusion, our data provide evidence that short-term aldosterone infusion enhances experimental arterial thrombosis in adrenalectomized diabetic rats. Prothrombotic effect of aldosterone seems to rely on both MR and GR receptors dependent pathways. These findings suggest alternative therapeutic strategies for modulating aldosterone actions on cardiovascular system.