Morphological Identification of TRPC7 in Cardiomyocytes From Normal and Renovascular Hypertensive Rats

OBJECTIVE:We aimed to investigate the expression characteristics of transient receptor potential canonical 7 (TRPC7) in normal and hypertrophic cardiac myocytes. METHODS:The 2-kidney 1-clip (2K1C) method was used to induce renovascular hypertension. Losartan, the potent inhibitor of angiotensin II (Ang II) receptor, was applied to the drinking water of 2K1C rats to inhibit Ang II-mediated responses. TRPC7 expression was examined by immunohisto/cytochemistry and Western blot analyses in normal and hypertrophic hearts. The expression level of protein kinase C (PKC), a negative regulator of TRPC7 channel in in vitro study, was also evaluated. RESULTS:In normal rat ventricles, strong TRPC7 immunoreactivity was distributed in the surface sarcolemma of cardiomyocytes, and a moderate but striated TRPC7 immunoreactivity was also detected in the subcellular regions. The 2K1C operation caused significant hypertension and cardiac hypertrophy as demonstrated by respective biophysical or biochemical assays. At this stage, expression of TRPC7 was significantly downregulated at both tissue and cell levels, whereas that of PKC was upregulated. Further analysis revealed a negative correlation between TRPC7 and PKC expression patterns. Oral application of losartan ameliorated the extent of experimentally induced hypertension and cardiac hypertrophy. Simultaneously, it effectively reversed the downregulation of TRPC7 and mildly antagonized the upregulation of PKC. CONCLUSIONS:Taken together, these results for the first time show that TRPC7 localizes in the surface and tubular sarcolemma of cardiomyocytes in normal adult rats and its expression significantly decreases in hypertrophied cardiomyocytes from renovascular hypertensive rats. TRPC7 may thus play a significant role in normal physiological settings in the heart.