Name: ANNA KAROLINA NASCIMENTO COSTA
Publication date: 31/08/2022
Advisor:
Name |
Role |
|---|---|
| EDUARDO HERTEL RIBEIRO | Advisor * |
| IVANITA STEFANON | Advisor * |
Examining board:
| Name |
Role |
|---|---|
| IVANITA STEFANON | Advisor * |
| NAZARE SOUZA BISSOLI | Internal Examiner * |
Summary: Testosterone is a vasoactive hormone, which acts by genomic and non-genomic mechanisms. Acutely, it may have endothelium-dependent vasodilatory actions. However, the long-term modulation of testosterone on the regulation of vascular tone remains unclear. The hypothesis of this study is that, in the long term, testosterone participates in the vascular reactivity regulation, dependent on the renin-angiotensin-aldosterone system.
Wistar rats (N=128), at 12 weeks of age, were divided into male Control (SHAM) and orchiectomy surgery (OQT), treated for 3 months with losartan, an angiotensin II receptor blocker (SHAM+LOS and OQT+ LOS), 15 mg/kg, s.c); spironolactone (SHAM+SPI and OQT+SPI, 80 mg/kg, gavage), mineralocorticoid receptor antagonist and apocynin, NADPH oxidase inhibitor (SHAM+APO and OQT+APO, 30 mg/kg, drinking water), Vascular reactivity was analysed in isolated aortic rings, as the percentage of response to KCl (75 mM), superfused with modified Krebs pH 7.4, 36.5oC. The presence of vascular presence was observed in vitro as curves-response to phenylephrine (10-11 to 10-3 M) and absence of: L-NAME, 100 μM; indomethacin (INDO, 10 μM) and endothelium-denuded rings (E-). Plasma lipid peroxidation was measured using the TBARS technique. (CEUA-UFES 017/2020). Results were expressed as mean ± SEM and using Student´s t test, analysis of variance (ANOVA), one way. The OQT groups, untreated and OQT treated with APO and LOS, had lower body weight at the end of the 3 months (SHAM 231 ± 11g; OQT= 158,4 ± 13,0g*; OQT+APO 208,3 ± 15,4g; OQT+LOS 156,0 ± 23,0g *p<0,05). The Rmax for phenylephrine was the same between the SHAM and OQT groups. Treatments for 3 months with LOS and APO did not change Rmax to phenylephrine. However, LOS treatment reduced the pD2 of the OQT group (log EC50: OQT= -6.240 ± 0.15 vs OQT+LOS= -7.218 ± 0.23 *p<0.01). Inhibition of MR receptors with spironolactone determined a lower maximal contraction to phenylephrine in the OQT group than in the SHAM, suggesting that this pathway could be testosterone dependent. (SHAM+SPI =120.4 ± 7.56% n=10 vs OQT+SPI= 93.3 ± 10.2% n=10; *p<0.05). Phenylephrine reactivity increased in the presence of L-NAME and in the absence of E, similarly between the groups. Inhibition of the COX pathway with indomethacin determined a reduction in Rmax in both groups (Rmax SHAM= 118.3 ± 8.04 vs SHAM+INDO = 56.27 ± 6.61, p <0.01 and OQT= 119.8 ± 8.41 vs OQT+INDO= 72.64 ± 9.34, p<0.01). There was no difference in reactivity between the groups incubated with indomethacin (SHAM+INDO and OQT+INDO). There was a reduction in RMax, in the presence of indomethacin, only in the OQT+SPI group. This result suggests the participation of aldosterone in the COX activation pathway, possibly of a vasoconstrictor, since in the SHAM+SPI group, indomethacin reduced the maximum contraction (Rmax: SHAM+SPI = 120.4 ± 7.56; OQT+ SPI= 93.28 ± 10.18; SHAM+SPI+INDO = 89.99 ± 8.45; OQT+SPI+INDO = 74.15 ± 7.92, * p <0.05). Endothelial NO bioavaliability seems to have been modified in the group treated with losartan, especially in the OQT+LOS-LN group, suggesting the importance of the testosterone pathway in the production of NO mediated by angiotensin II receptors. These data suggest that testosterone participates in the production of NO mediated by angio II, because when we remove the production of NO, through the LN, in the OQT group, there was a reduction in Rmax in relation to its control. Is suggests the importance of testosterone in the contractile response. mediated by the AT1 angiotensin receptor (Rmax: SHAM+LOS = 127.5 ± 5.63; OQT+LOS = 135.6 ± 4.74; SHAM+LOS LN = 183.4 ± 10.50; OQT+LOS LN = 151.8 ± 8.311; * p<0.05). The effects of treatment with the angiotensin II inhibitor, losartan, on rings without endothelium, showed that the endothelium injury caused an increase in the response to phenylephrine in the SHAM group. However, there was no difference between the OQT+LOS E- and OQT+LOS CT groups, suggesting a vasoconstrictor positive modulation that depends on the presence of angiotensin II. These data suggest that testosterone participates in the production of NO mediated by angio II, because when we remove the production of NO, through the LN, in the castrated group there is a reduction in Rmax in relation to its control, suggesting the importance of testosterone in the contractile response. mediated by the AT1 angiotensin receptor (Rmax: SHAM+LOS = 127.5 ± 5.63; OQT+LOS = 135.6 ± 4.74; SHAM+LOS LN = 183.4 ± 10.50; OQT+LOS LN = 151.8 ± 8.311; * p<0.05). The effects of treatment with the angiotensin II inhibitor, losartan, on rings without endothelium, showed that the endothelium injury caused an increase in the response to phenylephrine in the SHAM group. However, there was no difference between the OQT+LOS E- and OQT+LOS CT groups, suggesting a vasoconstrictor positive modulation that depends on the presence of angiotensin II. Orchidectomy modified the endothelium-dependent response during treatment with losartam (Rmax: SHAM+LOS = 127.5 ± 5.63; OQT+LOS = 135.6 ± 4.74; SHAM+LOS E- = 217.3 ± 217.3 ± 26.77; OQT+LOS E- = 145.3 ± 7.90. * p<0.05). In conclusion, the set of these results suggest the long term participation of testosterone and aldosterone in the modulation of vascular contraction induced by phenylephrine.
