Effects of metiamide on distribution of 14C-histamine in aortic smooth muscle

The effects of metiamide on 14C-histamine movements and on contractions induced by histamine were studied in rabbit aortic smooth muscle. Low temperature (0 degrees C) and pretreatment with aminoguanidine or chloroquine markedly reduced the uptake of 14C. Component analysis of 14C efflux curves indicated that this decrease occurred mainly within the slower of two washout components. Addition of metiamide (but not pyrilamine) to the bathing solution decreased 14C-histamine uptake, and exposure to metiamide during the washout of 14C-histamine decreased the rate of efflux. These effects of metiamide on 14C-histamine movements can be explained in terms of an altered ability of rabbit aortic smooth muscle to accumulate histamine at some cellular site or store.