Cardioprotective Solutions Exposure For 1 Hour in Hypoxia and Low Temperatures Affects Vascular Reactivity Differently

Abstract

Introduction: Heart preservation benefits cardiac performance after operations decreasing morbidity but the contribution of the vascular reactivity has been neglected.

Methods: We evaluated whether cardioprotective solutions, Krebs-Henseleit (KH), Bretschneider-HTK (BHTK), St. Thomas No. 1 (STH-1), and Celsior (CEL), affect vascular reactivity. Methods: Aortic rings from Wistar rats were used in two protocols. First, the rings were exposed to BHTK, STH-1 or CEL for 1 hour of hypoxia at 37 °C. Second, the rings were exposed to 10 °C or 20 °C for 1 hour under hypoxia. After treatment, the rings were immersed in KH at 37 °C, endothelial integrity was tested and concentration- response curves to phenylephrine were performed.

Results: In the first protocol, the solutions did not damage the endothelium; CEL and BHTK reduced KCl-induced contractions but not STH- 1; only CEL and BHTK reduced vascular reactivity; there was a positive correlation between Rmax and KCl concentration. At 20 °C, 1 hour under hypoxia, the solutions produced similar KCl-induced contractions without endothelial damage. CEL, BHTK and STH-1 decreased vascular reactivity. At 10 °C, STH-1 increased reactivity but CEL and BHTK decreased. After 1 hour under hypoxia in CEL or BHTK solutions, reactivity was similar at different temperatures. At 20 °C, endothelial damage after exposure to STH-1 produced more vasoconstriction than CEL and BHTK. However, at 10 °C, endothelial damage after CEL and BHTK exposure elicited more vasoconstriction while STH-1 showed a small vasoconstrictor response, suggesting endothelial damage.

Conclusion: STH-1 decreased reactivity at 20 °C and increased at 10 °C. CEL promoted greater endothelial modulation at 10 °C than at 20 °C, while STH-1 promoted higher modulation at 20 °C than at 10 °C. Vascular tone was reduced by CEL and BHTK exposure, also depending on the KCl concentration.

Keywords: Hypoxia; Endothelium; Phenylephrine; Temperature; Vasoconstriction; Vasoconstrictor Agents.

Fig. 1

Contractile response to potassium chloride (KCl-75 mM) in isolated aortic rings after 1 hour of hypoxia at 37 °C in Krebs-Henseleit (Krebs control), Celsior, Bretschneider-HTK (BHTK) or St. Thomas (ST) solutions. Results expressed as mean±SEM. *P<0,05 vs. Krebs-Henseleit (control), one-way ANOVA, Turkey test. The numbers in parentheses indicate the number of specimens used.

Fig. 2

Concentration-response curves to phenylephrine (PHE) in isolated aortic rings of Wistar rats after incubation for 1 hour in hypoxia with Celsior (A), Bretschneider-HTK (BHTK) (B) and St. Thomas (ST) (C) solutions, compared to the Krebs control solution, at 37 °C and after 1 hour of hypoxia. Results expressed as mean±SEM. *P<0.05 for comparison of Rmax vs. control Krebs, t-test. The numbers in parentheses indicate the number of specimens used.

Fig. 3

Correlation between Rmax and the potassium concentration of the studied solutions Krebs-Henseleit (Krebs control), Celsior, Bretschneider-HTK and St. Thomas-1. P<0.02.

Fig. 4

Concentration-response curves to phenylephrine (PHE) in isolated aortic rings of Wistar rats at 37 °C in Krebs-Henseleit (Krebs control) solution after incubation for 1 hour in hypoxia at 20 °C or 10 °C with Celsior (A and B) or Bretschneider-HTK (BHTK) (D and E) solutions in pD2 and Rmax values. In C (Celsior) and F (BHTK), comparisons of concentration-response curves at 20 °C or 10 °C. Results were expressed as mean±SEM. *P<0.05 vs. Krebs control solution, t-test for Rmax and pD2. The numbers in parentheses indicate the number of specimens used.

Fig. 5

Concentration-response curves to phenylephrine (PHE) in isolated aortic rings of Wistar rats at 37 °C in Krebs-Henseleit (Krebs control) solution after incubation for 1 hour in hypoxia at 20 °C (A) or 10 °C (B) of Rmax or pD2 of St. Thomas (ST) solution, compared to Krebs control solution, at 37 °C. In (C), comparison between concentration-response curves to PHE at 20 °C or 10 °C. Results expressed as mean±SEM. *P<0.05 vs. CT (control); t-test for Rmax and pD2. The numbers in parentheses indicate the number of specimens used.

Fig. 6

Concentration-response curves to phenylephrine (PHE) in the presence (E+) and absence of endothelium (E-) in isolated aortic rings of Wistar rats at 37 °C in Krebs-Henseleit solution, after incubation for 1 hour in hypoxia. In Krebs solution at 37 °C (A) and at 20 °C (B) or 10 °C (C) with the Celsior solution; comparison of endothelial modulation by calculating the difference of area below the curve (dAUC), in % (D). Results expressed as mean±SEM. In A, B and C, P<0.05 for comparisons of Rmax and pD2 at 37 °C, 20 °C or 10 °C, t-test. In D, *P<0.05 for comparisons of Krebs control vs. CEL at 20 °C or 10 °C, and #P<0.05 for comparisons of Krebs control vs. Celsior at 20 °C or 10 °C, one-way ANOVA, Tukey test. The numbers in parentheses indicate the number of specimens used.

Fig. 7

Concentration-response curves to phenylephrine (PHE) in the presence (E+) and absence of endothelium (E-) in isolated aortic rings of Wistar rats at 37 °C in Krebs-Henseleit solution, after incubation for 1 hour in hypoxia. In Krebs solution at 37 °C (A) and at 20 °C (B) or 10 °C (C) with the Bretschneider-HTK solution; comparison of endothelial modulation by calculating the difference of area below the curve (dAUC), in % (D). Results expressed as mean±SEM. In A, B and C, P<0.05 for comparisons of Rmax and pD2 at 20 °C or 10 °C, t-test. In D, *P<0.05 for comparisons of CT vs. Bretschneider-HTK at 37 °C, 20 °C or 10 °C, and #P<0.05 for comparisons of Krebs control vs. BHTK at 20 °C or 10 °C, one-way ANOVA, Tukey test. The numbers in parentheses indicate the number of specimens used.

Fig. 8

Concentration-response curves to phenylephrine (PHE) in the presence (E+) and absence of endothelium (E-) in isolated aortic rings of Wistar rats at 37 °C in Krebs-Henseleit solution, after incubation for 1 hour in hypoxia. In Krebs solution at 37 °C (A) and at 20 °C (B) or 10 °C (C) with St. Thomas solution; comparison of endothelial modulation by calculating the difference of area below the curve (dAUC), in % (D). Results expressed as mean±SEM. In (A) and (B), P<0.05 for comparisons of Rmax and pD2 at 37 °C, 20 °C or 10 °C, t-test. In (D), *P<0.05 for comparisons of Krebs control vs. St. Thomas at 20 °C or 10 °C, and #P<0.05 for comparisons of CT vs. St. Thomas at 20 °C or 10 °C, one-way ANOVA, Tukey test. The numbers in parentheses indicate the number of specimens used.