IngentaConnect The influence of transmural pressure and longitudinal stretch on ...

Abstract:

The aim of the study was to investigate transmural pressure and longitudinal stretch modulation of K⁺- and Ca²⁺-induced constriction of porcine conductance coronary arteries. In a pressure myograph set-up, left anterior descendent coronary arteries from 70 to 90 kg pigs were investigated at pressures from 20 to 120 mmHg. Longitudinal extension ratio (λ = L/L₀^-1, where L₀ is the in situ length and L the examination length) varied between 0.9 and 1.1. Two protocols were carried out: (1) Outer diameter response to maximal depolarization by K⁺ 125 mM at 20-120 mmHg and λ at 0.90-1.10. (2) Concentration-response curves with K⁺ (4.7-125 mM) and Ca²⁺ (0.05-4.0 mM) at four combinations of P and λ (P = 100 mmHg, λ = 0.9; P = 100 mmHg, λ = 1.1; P = 40 mmHg, λ = 0.9; p = 40 mmHg, λ = 1.1). Results: Endothelial function was preserved. A slight (<5% diameter reduction) basal tone and no myogenic response was found. Protocol 1: the constriction to K⁺ 125 mMwas maximal in a wide pressure range from 40 to 120 mmHg. Despite the fact that K⁺-induced diameter changes were statistically insignificant between 40 and 120 mmHg, there was a linear trend towards smaller diameter changes in this pressure range (r = -0.54, P < 0.01). Stretch influenced constriction at 20 mmHg because λ = 0.90 and 0.95 resulted in smaller diameter-reductions than λ = 1.00-1.10 (P < 0.05 for all). Contrastingly, at 120 mmHg the constriction at λ = 1.10 was smaller than the responses at λ = 0.90-1.05 (P < 0.05 for all). Protocol 2: EC₅₀ and EC₁₀ values for K⁺- and Ca²⁺ were generally higher (more sensitive) at 40 compared with 100 mmHg. Stretch was of no significant importance for EC₅₀ and EC₁₀ at 40 and 100 mmHg. It is concluded that porcine coronary artery constriction to non-metabolized agonists is maximal at 40 mmHg with a trend towards smaller diameter changes with higher pressures. Longitudinal stretch affects responsiveness at pressure extremes.

Keywords: calcium; coronary vessels drug effects; myograph; porcine; potassium; vascular physiology

Document Type: Research article

DOI: 10.1046/j.1365-201x.1999.00519.x

Affiliations: 1: Department of Cardiology, University Hospital Aarhus, Skejby Sygehus, Aarhus, Denmark 2: Institute of Pharmacology, University of Aarhus, Aarhus, Denmark 3: Imperial College School of Medicine, Department of Cardiology, Hammersmith Hospital, London, UK

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The influence of transmural pressure and longitudinal stretch on K+- and Ca2+-induced coronary artery constriction

The influence of transmural pressure and longitudinal stretch on K⁺- and Ca²⁺-induced coronary artery constriction