| Abstract: |
Addition of Ca2+ to primary cultures of female pituitary cells incubated in serum-free medium lacking added Ca2+ yielded no effects on levels of prolactin or growth hormone mRNA, assayed by cytoplasmic dot hybridization. However, incubation of the cells in serum-free medium containing sufficient ethylene glycol bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid to reduce medium Ca2+ levels below the 10-40 μM present as a trace contaminant yielded a decrease in the levels of both mRNAs. The decrease was dose-dependent at extracellular Ca2+ concentrations below 1.0 μM, had an apparent half-maximum at about 0.3 μM, and did not appear to plateau with increasing incubation times. Following 2-3-day incubations of cells in low Ca2+, a reduction of prolactin mRNA (23-70-fold) consistently greater than the reduction of growth hormone mRNA (9-15-fold) was observed. Similar effects of reduced extracellular Ca2+ were obtained with primary cultures of male pituitary cells. The specificity of these effects of lowered extracellular Ca2+ was demonstrated by the following observations. The decreases in these mRNAs were substantially reversible by readdition of Ca2+ to the incubation medium. Reduction of extracellular Ca2+ led to no detectable changes in cellular ribosomal RNA levels or overall RNA synthesis. In male pituitary cells, the level of another metal-regulated mRNA, that for metallothionein, was not decreased by a reduction of extracellular Ca2+ that caused a 40-fold decrease in levels of prolactin and growth hormone mRNA. Hence, Ca2+ exhibits specificity in its regulation of pituitary prolactin and growth hormone gene expression. |
| Keywords: |
dose response; nonhuman; animal cell; animal; cells, cultured; gene expression; calcium; transcription, genetic; in vitro study; growth hormone; kinetics; drug mechanism; cell culture; messenger rna; rna, messenger; nucleotide sequence; drug response; rat; drug tissue level; rats; radioisotope; drug determination; drug isolation; culture media; prolactin; magnesium; endocrine system; drug purification; pituitary gland; messenger rna synthesis; hypophysis cell; female; priority journal; support, u.s. gov't, p.h.s.; support, u.s. gov't, non-p.h.s.; egtazic acid; cell hybridization; preliminary communication; drug analysis; uridine h 3; growth hormone messenger ribonucleic acid; prolactin messenger ribonucleic acid
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