Effect of Propitocaine with Felypressin on Myocardial Blood Flow and Cardiac Output in Spontaneous Hypertensive Rats

We measured the effect of propitocaine with felypressin (FP) on myocardial blood flow and cardiac output in spontaneous hypertensive rats (SHR). This study was motivated by our desire to understand the influence of FP on circulatory dynamics in hypertensive patients. Experiment 1 ; Fifteen Wister rats were anesthetized with sodium pentobarbital (50 mg/kg, i. p.) and artificial ventilation via tracheotomy was performed. A catheter was inserted into the left ventricle from the common carotid artery for CMS injection. A catheter was inserted into the abdominal aorta for CMS collection. Blood collection was started at 1 ml blood, and 1 ml of blue CMS was immediately injected. FP (0.03 ml) was administered via labial gingiva. After 5 minutes, blood collection was started and yellow CMS was injected immediately. The blood samples were dissolved in 5 ml of 4N-NaOH and 1 ml of blood dissolution reagent. The extracted heart was dissolved by adding 20 ml of 4N-NaOH and 4 ml tissue blood dissolution reagent. Dissolved samples were filtered with a 10 μm hole filter and dried. After adding 1 ml of "N,N-dimethylformamide", the samples were centrifuged for 5 minutes at 5,000 rpm. The absorbances in top clear layer were measured for cardiac output and myocardial blood flow was calculated. The data was analyzed by paired-t test (p<0.05 considered significant). Administration of FP did not result in significant differences in myocardial blood flow, but cardiac output decreased significantly from 42.071 ± 22.766 ml/min to 34.633 ± 17.441 ml/min. Experiment 2 ; From experiment 1, we could measure myocardial blood flow and cardiac output in Wister rats using CMS. Next, we measured the effect of FP on SHR. Fifteen SHR were anesthetized and ventilated as in experiment 1. A catheter for CMS injection was inserted as in experiment 1. A catheter was inserted into the left femoral artery for CMS collection. A catheter was inserted into the right femoral artery for measurement of heart rate and blood pressure (Fig. 1). CMS injection and blood collection for measurement of cardiac output and myocardial blood flow were performed using the same method as in experiment 1. Furthermore, heart rate and blood pressure were measured just before injection of each of the blue and yellow CMS. The extracted heart was divided into left and right parts at the cardiac septum (Fig. 2). Tissue samples of the divided heart were dissolved by adding 10 ml of 4N-NaOH and 2 ml of tissue blood dissolution reagent. The blood and heart samples were filtered, dried, centrifuged and measured for absorbances as in experiment 1. Administration of FP did not result in significant differences in myocardial blood flow (Fig. 3, 4), but cardiac output decreased significantly from 52.796 ± 17.643 ml/min to 43.235 ± 15.030 ml/min (Fig. 5). Heart rate decreased significantly from 295.0 ± 30.3 beats/min to 291.1 ± 30.5 beats/min (Fig. 6), systolic blood pressure decreased significantly from 121.5 ± 29.3 mmHg to 114.5 ± 31.5 mmHg (Fig. 7), and diastolic blood pressure also decreased significantly from 70.9 ± 23.0 mmHg to 66.2 ± 24.5 mmHg (Fig. 8). In conclusion, we suggest that FP may have maintained oxygen supply in myocardial tissues by maintaining myocardial blood flow.