The effects of L-name and dexamethasone on smooth muscle response of the thoracic aorta in pregnant and non-pregnant rats

Hypertension is a common health problem and has a high risk for cardiovascular system disorders and kidney damage. Although it is a common problem, etiology of 95% of the cases is not yet known. To understand general and special effects of hypertension in humans and in pregnancy, respectively, various experimental models have been developed which include nitric oxide synthase (NOS) inhibition and glucocorticoid-induced hypertension models. With this study, it is aimed to investigate the changes in vascular smooth muscle responses in several hypertension models induced by N-nitro L-arginine methyl ester (L-NAME), dexamethasone (DEXA), and L-NAME + DEXA in Wistar albino female rats. In the study, a total of 62 pregnant and non-pregnant female Wistar albino rats were used in two simultaneous experiments. During vaginal sperm control, the day when spermatozoa were detected in vagina of 33 rats, was determined as the beginning of the pregnancy. Thirty-three pregnant rats and 29 non-pregnant rats were randomly divided into 4 groups. After the blood pressures were measured on the 15th day of gestation, the rats were given physiological saline (pregnant control), L-NAME (150 mg/kg/day), DEXA (100 μg/kg/day), and L-NAME + DEXA + 100 μg/kg/day). To collect samples and measure vascular smooth muscle responses at the same time, these procedures were performed simultaneously in non-pregnant rats, as well. Blood pressure were measured on day 19 of the experiment and rats were housed in individual metabolic cages for collection of 24-h urine samples. After urine samples were collected on day 20, rats were sacrificed under anesthesia and necropsy was performed in the rats. To record responses of vessel contraction and relaxation, the thoracic aorta was carefully removed and rings (~ 4-5 mm) from the vessel were sliced. Measurements were performed in organ bath. Changes in diastolic blood pressure of pregnant rats were statistically significant between group DEXA and group L-NAME + DEXA (P <0.05). In the study, 24-h urine volume was not affected by interventions. For the amount of protein in urine, the difference between group DEXA and group L-NAME + DEXA was found to be significant in pregnant rats (P=0,005). In the contraction responses induced by different phenylephrine concentrations (10-5 and 10-4 M), it was determined that the differences between the controls and group L-NAME + DEXA in the non-pregnant rats and between the controls and group DEXA in pregnant rats were significant (P<0.05). For maximal relaxation responses achieved after administration of different concentrations of acetylcholine (Ach) and sodium nitroprusside (SNP), there was no difference between groups in pregnant and non-pregnant rats. Key words: Hypertension, organ bath, thoracic aorta, L-NAME, DEXA.