Influence of sodium and potassium content on arterial responsiveness.

Vasoconstrictor responses to norepinephrine were determined during constant flow perfusion with warm Krebs solution in dog mesenteric arteries. The arteries were then stored 20—24 hours at 3°C in one of the following isosmotic solutions: Krebs, complex K (KC1, CaCl 2 , KHCO 3 , and glucose), NaCl, KC1, sucrose, or mannitol. After storage, arteries were again perfused with warm Krebs solution, and vasoconstrictor responses to norepinephrine compared to prestorage control responses. Tissue levels of Na + and K + were determined before cold storage and after 0—35 minutes of poststorage perfusion with warm Krebs solution. Storage of arteries in mannitol or sucrose solution reduced their Na + and K + content, and during poststorage perfusion with warm Krebs solution their responsiveness gradually improved as they rapidly (within 5 minutes) regained Na + and slowly regained K +. Arteries stored in NaCl solution were initially more responsive than those stored in electrolyte-free solutions during poststorage perfusion with warm Krebs solution, and their responsiveness also improved as they regained K +. Arteries cold-stored in K +-containing media (KC1 and complex K solutions) quickly regained Na + , and their responsiveness exceeded prestorage values with 11 minutes of poststorage perfusion with warm Krebs solution. Since these data indicate that artery responsiveness may be related to tissue levels of both Na + and K + , efforts were made to establish minimal levels of each ion required for "normal" responsiveness. The critical level of Na + appears to be approximately 30 /tEq Na/g dry weight; the minimal effective K + content is apparently near 20 /xEq K/g dry weight. If arteries contain at least minimal levels of K + and an excess (over 100 yuJEq/g) of Na + , the magnitude of their responses to vasoconstrictor stimuli is exaggerated. KEY WORDS norepinephrine sodium depletion cold storage epinephrine isolated arteries perfused arteries potassium depletion vasoeonstricrion dog mesenteric arteries • When vascular smooth muscle is refrigerated in physiological salt solution overnight or longer, vascular response to vasoconstrictor stimuli is often increased. Artery segments stored in cold salt solutions tend to increase their intracellular sodium ion content at the expense of intracellular potassium (1, 2). These facts pose the question of the relationship between the vascular smooth muscle ion content and vascular responsiveness, and at the same time suggest the possible means of exploring this relationship. Any direct correlation between tissue or cellular ionic composition and arterial …