Cytochemical localization of Na+/K(+-)ATPase activity in cochlear strial marginal cells after various catecholamine administrations

Sodium/potassium-activated adenosine triphosphatase (Na+/K+-ATPase) activit y in the kidney and brain is high, and is regulated by catecholamines. Na+/ K+-ATPase activity is also high in the basolateral infoldings of the strial marginal cells, where it aids in maintaining the characteristic electrolyt e composition of the endolymph. To clarify the involvement of humoral contr ol in strial function, particularly the role of catecholamines, the K+-depe ndent p-nitrophenylphosphatase (K+-NPPase) activity of strial marginal cell s was investigated in guinea pigs using a cerium-based cytochemical method. The effects of reserpine, serotonin (5-HT), norepinephrine (NE), epinephri ne (EP), both alone and in combination, were studied. High doses of reserpi ne cause depletion of sympathetic substances. Strial K+-NPPase activity was decreased after reserpine or doparnine treatment, and was increased after 5-HT, NE, and EP treatment. After reserpinization, repeated treatment with 5-HT, NE, or EP led to detectable strial enzyme activity. Thus, exogenous 5 -HT, NE, and EP were able to restore strial K+-NPPase activity in the reser pine-treated animals. These results suggested that biogenic amines regulate strial K+-NPPase activity. Thus, the function of the stria vascularis may be regulated by the opposing actions of these catecholamines, and 5-HT.