Vasodilatation of renal hypertensive rat coronary artery induced by the compound that combines NO donor and COX inhibitor (NCX2121)
Authors: Bendhack Lusiane Maria , de Paula Tiago Dal‐Cin , Grando Marcella Daruge 
Published: November 2023

Vascular tone is modulated by the production and/or release of relaxing factors like NO and constrictor factors such as reactive oxygen species (ROS) and COX products like thromboxane A2 (TXA2). It is particularly important in coronary arteries for the proper cardiac function. However, in cardiovascular diseases like hypertension, there is an imbalance with decreased NO bioavailability and increased TXA2 produced by COX and ROS produced by NADPH‐oxidase. Then, the use of the compound NCX2121, that is a combination of COX inhibitor (indomethacin) and NO donor could be an important pharmacological approach. This study aimed to evaluate the vasodilatation induced by NCX2121 in coronary arteries from renal hypertensive (2K‐1C) and normotensive (2K) rats. All the animal procedures were approved by the Ethics Committee of the University of São Paulo. Male rats were submitted to renovascular hypertension (2K‐1C) and another group of rats was submitted to sham‐operation (2K). After six weeks the systolic blood pressure was measured and the 2K‐1C were considered hypertensive when the systolic arterial pressure was ≥ 160 mmHg. The rats were killed and septal coronary arteries were isolated. The vessels were mounted in myograph to microvessels, submitted to the normalization process and stimulated with KCl (120 mM). The endothelium viability was tested with acethylcholine (ACh, 10 μM). The preparations were washed and concentration‐effect curves were constructed for the TXA2 analogue that is a TP receptor agonist (U46619). On top of the maintained contraction to U46619, concentration‐effect curves to NCX2121 were constructed in the absence (control) or after incubation with apocynin (1 μM). The internal diameter, the maximum contraction and relaxation (ME) were evaluated. The coronary arteries from 2K‐1C and 2K were collected, frozen and stored at −80° C to measure the COX‐1 and COX‐2 expression (arbitrary units) by Western Blot. COX‐1 was expressed in a similar way in 2K‐1C (0.19 ± 0.05) and 2K (0.07 ± 0.01). However, COX‐2 expression was higher in 2K‐1C (0.29 ± 0.07, n=7, P<0.05) than in 2K (0.11 ± 0.01, n=7). The internal diameter was not different between 2K‐1C (296.6 ± 19.2 μm, n=11) and 2K (287.9 ± 26.6 μm, n=9). The contraction to KCl was not different in 2K‐1C (3.2 ± 0.4 mN) and 2K (3.7 ± 0.4 mN). However, the contraction to U46619 was lower in 2K‐1C (2.8 ± 0.9 mN, n=6, P<0.05) than in 2K (6.3 ± 0.8 mN, n=6). NCX2121‐induced relaxation was similar in 2K‐1C (ME: 37.2 ± 6.9% n=6) and 2K (ME: 20.8 ± 4.5%, n=5), which effect was not changed by apocynin. Taken together, the results indicate that the coronary artery relaxation induced by NCX2121 is normalized in renal hypertensive rats. Also our results suggest that the high COX‐2 expression would be involved in U46619 lower contraction in 2K‐1C coronary arteries. ROS are not involved in NCX2121‐induced relaxation.

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