“…The [3H]ouabain is found in a lysosomal fraction and is then released unchanged from the cells, presumably by exocytosis, with a half-time of about 70h (Pollack et al,198 la; Cook et al, 1982). The inactivated, internalized, pumps are replaced (Boardman et al, 1972) at a rate which is at least 4-fold higher than the turnover rate in the absence of ouabain (Lamb & Ogden, 1982) but slower than the internalization rate (Lamb & Ogden, 1982). As a result, the receptor are downregulated in the presence of cardioactive steroids (Aiton et al, 1981).…”