Decreased Calcium Pump Activity in Duodenal Epithelial Cells from Spontaneously Hypertensive Rats

Summary

Abstract. Recently, hypertension research has focused on altered cytosolic free Ca²⁺, [Ca²⁺]i, in cells of spontaneously hypertensive rats (SHR). In this work, a mechanism(s) responsible for regulating [Ca²⁺]i was studied with duodenal epithelial cells isolated from SHR and their control, normotensive Wistar-Kyoto rats (WKY). The equal specific activity of sucrase, an enzyme characteristic of microvilli, in both mucosal scrapings and isolated cells from SHR and WKY suggested that mucosal density of enterocytes was not largely different between the two strains. [Ca²⁺]i of the isolated cells was estimated with fura-2. Upon incubation in the presence of CaCl₂, [Ca²⁺], increased to a larger extent in SHR than in WKY cells. Ca²⁺ efflux based on measurements of [Ca²⁺]1 was decreased in SHR cells. Correspondingly, it was found that ⁴⁵Ca efflux at 10 sec was lower for SHR cells than for WKY cells. Specific activities of Ca²⁺-stimulated and Ca²⁺/calmodulin-stimulated ATPases in basolateral plasma membrane preparations were reduced in SHR cells. These results indicated that Ca²⁺ efflux was decreased by reduction in Ca²⁺-pumping ATPase activity in SHR enterocytes.