Beneficial effects of calcium channel blockers and calmodulin binding drugs on in vitro renal cell anoxia.

Proximal tubules (PSTs) of the S1, S2 and S3 segments and cortical collecting tubules (CCTs) were microdissected individually from rabbit kidneys and cultured for 7 days in hormonally defined media. Anoxia was induced by incubation of cultures in normal medium for 45 min at 25 degrees C in an atmosphere of nitrogen and cell death was measured by nigrosine dye uptake. After 45 min of anoxia and a 4- to 6-hr incubation in normal Ca++-containing media, cells from all segments were dead. Addition of calcium channel blockers verapamil and nifedipine (5 X 10(-7) and 10(-6) M, respectively) for the first 2 hr after anoxia to the incubation media was associated with a 60 +/- 8 and 33 +/- 7% survival of PST cells (5 hr after anoxia), p less than .05. Verapamil at 5 X 10(-8) M caused a 42 +/- 4% survival whereas nifedipine at 10(-7) M was not effective on the survival rate of PST cells (5 hr after anoxia). These calcium channel blockers also afforded protection from anoxic cell death for CCT cells. The role of calmodulin in anoxic cell injury was studied by means of calmodulin binding drugs, trifluoperazine and W7 [N-(6-aminohexyl)-5-chloronapthalene-sulfonamide]. Addition of trifluoperazine (5 X 10(-7) M) and W7 (5 X 10(-7) M to both PST and CCT cells during the 2-hr reflow period after 45 min of anoxia increased viability by 58 +/- 3 and 62 +/- 3%, respectively (P less than .05) at 5 hr postanoxia.(ABSTRACT TRUNCATED AT 250 WORDS)