HEMORHEOLOGICAL CHANGES INDUCED BY ATRIOPEPTIN-III IN ANESTHETIZED RATS

Intravenous injection of atriopeptin III (AP III) into anesthetized rats produced a marked fall of mean blood pressure (-12 +/- 2 %, p < 0.01) and significant increases in hematocrit from 45.1 +/- 2.7 (mean +/- SD) to 48.8 +/- 2.6 % (p < 0.01), plasma viscosity from 1.4 +/- 0.1 to 1.6 +/- 0.2 mPa.s (p < 0.05), blood viscosity at both low and high shear rates from 22.3 +/- 4.7 to 29.4 +/- 3.7 mPa.s (p < 0.01) and from 7.2 +/- 1.1 to 8.3 +/- 0.8 mPa.s (p < 0.05), respectively. Meanwhile, erythrocyte aggregation, erythrocyte rigidity and electrophoretic mobility changed insignificantly. The afore-mentioned effects of AP III could not be modified by bilateral nephrectomy. In bilaterally nephrectomized rats, total serum protein changed from 5.78 +/- 0.27 of saline control to 5.86 +/- 0.18 g 100ml-1 (p > 0.05), while albumin content slightly decreased from 3.25 +/- 0.10 to 2.85 +/- 0.09 g 100ml-1 (p > 0.05) 20 min after AP III administration. The results suggest that AP III exerts acute action on rheological property of blood but not that of erythrocyte. The reduced circulating plasma volume together with the increased blood viscosity, independent of an intact renal function, may contribute to the AP-induced decrease in venous return.