AUTHOR=Fioretti Alexandre C. , Dsouki Nuha A. , do Vale Barbara , de Carvalho Rodrigo P. , Dias Daniel P. M. , Venancio Daniel P. , Fonseca Fernando L. A. , Sato Monica A. 

TITLE=Vitamin D supplementation at different doses affects the vagal component of the baroreceptor reflex and the Bezold-Jarisch reflex in eutrophic rats

JOURNAL=Frontiers in Physiology

VOLUME=Volume 13 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2022.934625

DOI=10.3389/fphys.2022.934625

ISSN=1664-042X

ABSTRACT=Vitamin D has been used to prevent several diseases. The 1,25 (OH) 2D3, the active form of vitamin D (VitD), participates in calcium metabolism, and has direct action in various tissues binding to the VitD receptor. We investigated whether the supplementation with different doses of VitD affect or not the resting mean arterial pressure (MAP) and heart rate (HR), heart rate variability (HRV), baroreceptor and Bezold-Jarisch reflexes in eutrophic rats. Adult male Wistar rats were randomly assigned in 4 groups (Control, VitD 15, 250 and 3750 IU/day, n=6/group). After 3 days of supplementation, MAP and HR recordings were performed in conscious rats. Resting MAP, HR and HRV showed no difference in Control and VitD groups. Nevertheless, the index of the baroreflex showed that the bradycardic component of the baroreflex evoked by a pressor dose of phenylephrine (3 µg/kg of b.w.) in bolus injection had a significant increase in rats supplemented with VitD 15 IU/day for 3 days compared to Control animals. The index of the baroreceptor reflex evaluated with bolus injection of a depressor dose of sodium nitroprusside (30 µg/kg of b.w.) showed that the tachycardic component of the baroreflex is not different comparing all groups supplemented with VitD and Control animals. Rats supplemented with VitD 15 IU/day presented exaggerated bradycardic responses to the intravenous injection of phenylbiguanide (PBG, 5 µg/kg of b.w.) compared to Control animals, despite the similar hypotension in both groups. Higher doses of supplementation of VitD (250 and 3750 IU/day for 3 days) abolished the hypotension and bradycardia induced by PBG. Therefore, the supplementation with VitD (15, 250 and 3750 IU/day) for 3 days did not affect the resting MAP, HR and autonomic modulation on the heart in rats. Despite that, the low dose of VitD (15 IU/day for 3 days) improved the sensitivity of the bradycardic component of the baroreflex, whereas higher doses of supplementation with VitD (250 and 3750 IU/day for 3 days) were unable to cause such effect. In addition, the Bezold-Jarisch reflex responses can be affected regardless the dose of VitD (15, 250 or 3750 IU/day) supplementation for 3 days in rats..