NCX1 Na/Ca exchanger splice variants in pancreatic islet cells

In the rat pancreatic beta -cell, Na/Ca exchange displays a quite high capa city. The cell is equipped with two alternatively spliced Na/Ca exchanger-1 (NCX1) isoforms, namely NCX1.3 and NCX1.7. To examine the existence of a p ossible functional difference between these splice variants, they were clon ed, together with the heart variant NCX1.1, and expressed in human embryoni c kidney-293 (HEK293) and Chinese hamster ovary (CHO) cells. In these two s ystems, the three splice variants showed a comparable level of intracellula r Na+ (Na-i(+))dependent extracellular Ca2+ (Ca-o(2+)) uptake. Different le vels of NCX1.3 and NCX1.7 transcripts were found in four rodent species, to gether with a marked interspecies difference in Na/Ca exchange activity. Th ree additional splice variants were found (NCX1.2, NCX1.9 and NCX1.13) in g uinea-pigs, hamsters and mice, again in different proportions. Our data pro vide evidence for the activity of the three NCX1 splice variants. They also show the existence of a differential and species-specific transcription pa ttern of NCX1 gene products in pancreatic islet cells.