Nitrendipine-induced stimulation of renin release by the isolated perfused rat kidney. 
The direct effects of the organic calcium antagonist nitrendipine upon renin release were assessed using the isolated rat kidney perfused at constant pressure.  This model circumvents the indirect actions of vasodilating agents by artificially maintaining perfusion pressure constant, thereby avoiding the hypotensive effects associated with the systemic administration of such agents.  Renin release as assessed by radioimmunoassay was stimulated 2.6-fold upon the administration of 10(-6) M nitrendipine.  Since this stimulation of renin release occurred in the absence of any alteration in perfusion pressure, we conclude that it represents a direct action of nitrendipine.  This finding is in support of the current hypothesis concerning the inverse relationship between cytosolic Ca2+ and renin secretory rate, and suggests that Ca entry into the juxtaglomerular cells of the juxtaglomerular apparatus is sensitive to blockade by organic calcium antagonists such as nitrendipine.