C-TYPE NATRIURETIC PEPTIDE EFFECTS ON VASCULAR REACTIVITY IN HYPERTENSION. PARTICIPATION OF NITRIC OXIDE SYSTEM

M.A. COSTA; C. CANIFFI ; D. SUAREZ DI SALVO ; F. MENDES GARRIDO; M. CERNIELLO; C. ARRANZ

MILAN

Congreso; 21st EUROPEAN MEETING ON HYPERTENSION AND CARDIOVASCULAR PREVENTION; 2011

In previous studies we demonstrated that C-type natriuretic peptide (CNP) acute infusion reduces blood pressure and increases nitric oxide (NO) synthase (NOS) activity in spontaneously hypertensive rats (SHR). The aim was to study the participation of NO in the mechanisms involved in vascular relaxation induced by CNP in SHR. Methods: Aorta thoracic segments of 3-5 mm from Wistar (W) and SHR, were suspended in Krebs solution at 37ºC and gassed (95% O2 - 5% CO2, pH:7,4). The aortic rings were allowed to equilibrate for 60 min. and readjusted to basal tension 1 g. Isometric tension (g) was recorded by a forcetransducer, in presence of: phenylephrine (PE, 10-8-10-5 M), CNP (10-11-10-6 M) and LNAME (NOS inhibitor, 10-5 M). Endothelium integrity was verified with acethylcholine (ACh, 10-10-10-5 M). Aortic NOS activity (pmol 14C L-citrulline/g tissue.min) was determined.2 - 5% CO2, pH:7,4). The aortic rings were allowed to equilibrate for 60 min. and readjusted to basal tension 1 g. Isometric tension (g) was recorded by a forcetransducer, in presence of: phenylephrine (PE, 10-8-10-5 M), CNP (10-11-10-6 M) and LNAME (NOS inhibitor, 10-5 M). Endothelium integrity was verified with acethylcholine (ACh, 10-10-10-5 M). Aortic NOS activity (pmol 14C L-citrulline/g tissue.min) was determined.-8-10-5 M), CNP (10-11-10-6 M) and LNAME (NOS inhibitor, 10-5 M). Endothelium integrity was verified with acethylcholine (ACh, 10-10-10-5 M). Aortic NOS activity (pmol 14C L-citrulline/g tissue.min) was determined.-5 M). Endothelium integrity was verified with acethylcholine (ACh, 10-10-10-5 M). Aortic NOS activity (pmol 14C L-citrulline/g tissue.min) was determined.-10-10-5 M). Aortic NOS activity (pmol 14C L-citrulline/g tissue.min) was determined. Results: Basal NOS activity was higher in SHR and CNP increases this activity in both groups (W Basal: 208±12; W CNP: 311±10*; SHR Basal: 366±21*; SHR CNP: 429±25#). The increase of NOS activity induced by CNP in SHR was lower compared with W(W (CNPBasal): 103±11; SHR (CNP-Basal):65±7^). *p<0,01 vs Basal W; #p<0,01 vs Basal SHR; ^p<0,01 vs W, n=8. Table: Maximal relaxation (Rmax) and concentration of the CNP (expressed as negative log molar) producing 50% of maximum relaxation (pEC50) *p<0,01 vs W CNP, n=6. ANOVA followed by Bonferroni?s post-hoc test. Wistar rings have enhanced response to CNP compared with SHR. In normotensive ones, pre-treatment with L-NAME attenuated relaxant effects to CNP, indicating that NO would participate in CNP vasodilatory response in PE pre-constricted rings. In aorta rings of SHR, that have less maximal response to CNP, NOS inhibition with L-NAME had no significant effect on the relaxation induced by CNP. Conclusions: In normotensive rats, NO system would participate in arterial relaxation induced by CNP. The diminished vascular relaxation to CNP in SHR is probably due to an impaired response of NO-system.NOS activity was higher in SHR and CNP increases this activity in both groups (W Basal: 208±12; W CNP: 311±10*; SHR Basal: 366±21*; SHR CNP: 429±25#). The increase of NOS activity induced by CNP in SHR was lower compared with W(W (CNPBasal): 103±11; SHR (CNP-Basal):65±7^). *p<0,01 vs Basal W; #p<0,01 vs Basal SHR; ^p<0,01 vs W, n=8. Table: Maximal relaxation (Rmax) and concentration of the CNP (expressed as negative log molar) producing 50% of maximum relaxation (pEC50) *p<0,01 vs W CNP, n=6. ANOVA followed by Bonferroni?s post-hoc test. Wistar rings have enhanced response to CNP compared with SHR. In normotensive ones, pre-treatment with L-NAME attenuated relaxant effects to CNP, indicating that NO would participate in CNP vasodilatory response in PE pre-constricted rings. In aorta rings of SHR, that have less maximal response to CNP, NOS inhibition with L-NAME had no significant effect on the relaxation induced by CNP. Conclusions: In normotensive rats, NO system would participate in arterial relaxation induced by CNP. The diminished vascular relaxation to CNP in SHR is probably due to an impaired response of NO-system.(CNPBasal): 103±11; SHR (CNP-Basal):65±7^). *p<0,01 vs Basal W; #p<0,01 vs Basal SHR; ^p<0,01 vs W, n=8. Table: Maximal relaxation (Rmax) and concentration of the CNP (expressed as negative log molar) producing 50% of maximum relaxation (pEC50) *p<0,01 vs W CNP, n=6. ANOVA followed by Bonferroni?s post-hoc test. Wistar rings have enhanced response to CNP compared with SHR. In normotensive ones, pre-treatment with L-NAME attenuated relaxant effects to CNP, indicating that NO would participate in CNP vasodilatory response in PE pre-constricted rings. In aorta rings of SHR, that have less maximal response to CNP, NOS inhibition with L-NAME had no significant effect on the relaxation induced by CNP. Conclusions: In normotensive rats, NO system would participate in arterial relaxation induced by CNP. The diminished vascular relaxation to CNP in SHR is probably due to an impaired response of NO-system.(CNP-Basal):65±7^). *p<0,01 vs Basal W; #p<0,01 vs Basal SHR; ^p<0,01 vs W, n=8. Table: Maximal relaxation (Rmax) and concentration of the CNP (expressed as negative log molar) producing 50% of maximum relaxation (pEC50) *p<0,01 vs W CNP, n=6. ANOVA followed by Bonferroni?s post-hoc test. Wistar rings have enhanced response to CNP compared with SHR. In normotensive ones, pre-treatment with L-NAME attenuated relaxant effects to CNP, indicating that NO would participate in CNP vasodilatory response in PE pre-constricted rings. In aorta rings of SHR, that have less maximal response to CNP, NOS inhibition with L-NAME had no significant effect on the relaxation induced by CNP. Conclusions: In normotensive rats, NO system would participate in arterial relaxation induced by CNP. The diminished vascular relaxation to CNP in SHR is probably due to an impaired response of NO-system.W, n=8. Table: Maximal relaxation (Rmax) and concentration of the CNP (expressed as negative log molar) producing 50% of maximum relaxation (pEC50) *p<0,01 vs W CNP, n=6. ANOVA followed by Bonferroni?s post-hoc test. Wistar rings have enhanced response to CNP compared with SHR. In normotensive ones, pre-treatment with L-NAME attenuated relaxant effects to CNP, indicating that NO would participate in CNP vasodilatory response in PE pre-constricted rings. In aorta rings of SHR, that have less maximal response to CNP, NOS inhibition with L-NAME had no significant effect on the relaxation induced by CNP. Conclusions: In normotensive rats, NO system would participate in arterial relaxation induced by CNP. The diminished vascular relaxation to CNP in SHR is probably due to an impaired response of NO-system. W CNP W L-NAME+CNP SHR CNP SHR L-NAME+CNP Rmax (%) 103.3±5.3 64.5±6.9* 72.5±1.9* 61.3±8.8 pEC50 9.6±0.9* 6.4±1.2* 6.8±1.2* 6.3±0.9