Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
Board

Essential hypertension in humans and most animal models of hypertension is characterized by an increased peripheral vascular resistance. The cause of the resistance increase is the subject of intensive ongoing research. A common feature of human essential hypertension and animal models of primary hypertension is an arteriolar and capillary rarefaction. We have previously proposed that rarefaction is the consequence of inhibited vascular growth during early development. The purpose of the present study was to investigate the consequence of various patterns of arteriolar growth on resistance properties of the vascular network. For this purpose we recorded the topological development of a growing arteriolar network in the chick embryo chorio-allantoic membrane (CAM) at day 7, 10 and 14 of gestation, and measured diameter and length of the vessel segments. By applying Poiseuille's law and assuming all precapillary pressures to be equal, resistance (R) to flow was calculated. The number of segments increased from 543 to 1630 and 2757 on days 7, 10 and 14, whereas R decreased from 466 to 458 and 406 pa.mm-3 at the respective days. By applying a mathematical model, we could explain this pattern by assuming that the growth process is dominated in the first stage by segmental growth(SG),i.e. addition of segments in between branch nodes, and with time converged towards terminal growth(TG), i.e. addition to the most distal part. Adding 250 segments to the day 7 arteriolar tree according to TG increased resistance by 53%, whereas adding according to SG decreased resistance by 7%. Adding 750 segments to the day 10 tree according to TG increased resistance by 23%, whereas adding according to SG decreased resistance by 6%. We conclude that SG decreases and TG increases resistance. The magnitude of the resitance change depends on tree size and the site where the vessels are coupled to the existing tree. Thus, our study shows that the pattern of early arteriolar growth may have important long-term consequenses for the resistance properties of an arteriolar network.

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Presentation Number SAstruijker-boudier 0662
Keywords: arteriole, resistance, angiogenesis, hypertension