Expression of Ca 2+ Transport Genes in Platelets and Endothelial Cells in Hypertension

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Abstract
—Altered Ca 2+ handling is observed in different cells in essential hypertension. We investigated the expression of sarco(endo)plasmic reticulum Ca 2+ -ATPase (SERCA) and inositol 1,4,5-trisphosphate receptor (IP 3 R) isoforms in platelets and aortic endothelial cells (EC) isolated from spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats by ratio reverse-transcriptase—polymerase chain reaction (RT-PCR) analysis and Western blotting. SERCA2b and SERCA3 were assessed at mRNA (EC and platelets) and at protein level (platelets). IP 3 R1, IP 3 R2, and IP 3 R3 mRNAs were demonstrated in both cell types, but only IP 3 R1 and IP 3 R2 proteins were detected in platelets. Compared with WKY, SHR EC and platelets showed higher SERCA3 and IP 3 R2 expression and lower IP 3 R1 expression. We then investigated the effect of lisinopril (20 mg · kg − 1 · d − 1 ; 10-week treatment of 4-week-old rats or 2-week treatment of adult rats) and captopril (100 mg · kg − 1 · d − 1 ; 2-week treatment of adult rats). Consequently, expression patterns of SERCAs and IP 3 Rs were significantly modified. Except for SERCAs mRNA in platelets, all differences between SHR and WKY disappeared. However, SERCA3 remained the predominant isoform. Both EC and platelets demonstrated a high equal expression of IP 3 R2 mRNA. IP 3 R1 was the predominant platelet protein isoform, as it was in untreated WKY. mRNA was also isolated from pancreatic islets of WKY and SHR, but no effect of either rat strain or of lisinopril treatment was observed on the expression of the studied genes. We hypothesize that the identical expression pattern of SERCAs and IP 3 Rs after treatment with ACE inhibitors represents a different nonhypertensive configuration, which, through changes in intracellular Ca 2+ handling, improves endothelial and platelet dysfunction in SHR but has no effect in WKY.