K252a, another protein kinase inhibitor preventing Na-K-2Cl cotransport stimulation in a variety of cells (40 , 42), also in- hibited SPAK activity, although requiring slightly higher con- centrations than staurosporine.
arsenite, which stimulates stress-activated protein kinases (27) and mapks (32) and markedly activates na-k-2cl cotransport in ferret red cells (17), had little effect on spak autophosphorylation.