Injection of @entity291 parathyroid poly(A)+ RNA into XXXX oocytes confers sensitivity to high extracellular calcium.

@entity1238 @entity15410 @entity24585 @entity6372 @entity8594 @entity141 @entity291
Parathyroid cells detect increments in the extracellular [ @entity141 ], which lead to substantial increases in intracellular free @entity141 ([ @entity141 ]i) and, ultimately, to suppression of @entity24585 ( @entity24585 ) secretion. To determine whether mRNA from parathyroid tissue could confer sensitivity to high extracellular @entity141 , we isolated and injected total @entity291 parathyroid poly(A)+ RNA into @entity1238 oocytes. To assess translational activity of the RNA, @entity24585 released into the media was measured. Intact @entity24585 was detected in the medium for < or = 48 h, and injection of increasing amounts of RNA (approximately 0.5-50 ng/oocyte) led to the release of greater quantities of @entity24585 . We screened for the expression of a putative @entity141 sensor molecule by measuring 45Ca efflux from preloaded oocytes, in response to raising extracellular [ @entity141 ] from 0.7 to 5.7 mM. This increment in [ @entity141 ] stimulated 45Ca efflux by 249 +/- 52 cpm over 20 min from eggs injected with parathyroid poly(A)+ RNA (n = 22). This response was significantly greater than 45Ca efflux from any group of controls exposed to the same change in extracellular @entity141 (p < 0.02), including oocytes injected with either water, cRNA for the platelet-derived growth factor (PDGF) BB receptor, or T cell poly(A)+ RNA. Size-fractionation of poly(A)+ RNA over sucrose gradients demonstrated that mRNA, which induced @entity6372 to high extracellular @entity141 , was present in fractions with transcripts of approximately 5-9 kB. Injection of these fractions also conferred sensitivity to the presence of @entity8594 or @entity15410 (both at 5 mM) in the media.(ABSTRACT TRUNCATED AT 250 WORDS)
