Fig. 5. Effects of buffer composition on the response of efferent branchial arteries to addition of 40 mmol l^–1 NH₄Cl (intracellular alkalosis) and NH₄Cl washout (Wash; intracellular acidosis) 30 min later. Addition of 10 mmol l^–1 NaHCO₃ to Hepes (Hepes +HCO₃^–) did not affect the contraction accompanying NH₄Cl addition or washout, whereas in Cortland buffer, addition of NH₄Cl produced a significant relaxation () and washout produced a contraction that was significantly greater than the corresponding contraction in either Hepes or Hepes + HCO₃^– (*). Values are means ± s.e.m.; Hepes (N=14), Hepes+HCO^–₃ (N=4), Cortland (N=8).