Intraluminal Pressure and Ionic Distribution in the Tail Artery of Rats

Abstract

The relationship between changes in perfusion pressure and ionic transfers in the vascular wall has been studied using the rat tail vascular bed perfused at constant flow rate. Perfusion pressure was increased by elevating venous pressure, or by infusing norepinephrine. The ensuing ionic shifts were monitored by means of Na + and K + electrodes. In both instances, the rise in pressure was associated with ionic redistribution measured as a gain in K + and a loss in Na + in the perfusing medium. The increase in pressure showed a close correlation with K + efflux from the vascular wall, and a somewhat more variable correlation with Na + influx. While the qualitative aspect of the ionic transfers was similar in the two conditions, their size differed. It was much larger during a rise in pressure induced by venous back pressure, in which condition the wall tension was also proportionately larger. The occurrence of ionic transfers in response to changes in transmural distending pressure was confirmed in the isolated artery, perfused in situ. It is suggested that vascular tension is directly related to step levels of transmembrane ionic distribution, and that this distribution is regulated by passive stretch.