Expression of the diverse subtypes of inositol 1, 4, 5-trisphosphate (InsP3) receptor (IP3R) was examined in rat adrenal glomerulosa cells. The polymerase chain reaction products were characterized by means of DNA sequencing and/or restriction enzyme mapping. The predominant subtype expressed is IP3R-1; its alternatively spliced variants containing and lacking segment S1 are present in comparable amounts. The expression level of IP3R-2 is about a quarter that of IP3R-1, whereas IP3R-3 is expressed at a very low level. Sodium depletion, a chronic physiological stimulus of glomerulosa cells, failed to influence the expression of IP3R-1, as measured by competitive polymerase chain reaction, and failed to modify the ratio of the different receptor subtypes, as studied with restriction enzyme mapping.
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