Expression of LDL receptor, apolipoprotein B, apolipoprotein A-I and apolipoprotein A-IV mRNA in various mouse organs as determined by a novel RNA-excess solution hybridization assay.

We report expression of LDL receptor, apolipoprotein B (apoB), apolipoprotein A-I (apoA-I) and apolipoprotein A-IV (apoAIV) mRNA in various mouse organs. These mRNA were quantified by an RNA-excess solution hybridization assay. For preparing specific probes, we cloned cDNA fragments of rat LDL receptor, apoB and apoA-I and mouse apoA-IV into the polylinker region of pGEM3Zf(+) and used the recombinant vectors for preparing 32P-labeled cRNA probes as well as RNA standards using the T7 and SP6 promoters flanking the polylinker regions. Preparation of cRNA probes and RNA standards is faster and more convenient than preparing cDNA probes and ssDNA standards. Absolute levels of mRNA were quantified in the liver, intestine, kidney, heart, lung, spleen and adrenals of females of two mouse strains. C3H/HeJ and C57BL/6J. ApoB, apoA-I and apoA-IV genes in mice are expressed in the liver and intestine and LDL receptor gene is expressed mainly in liver, intestine and adrenals. ApoA-I mRNA levels were found to be 730 and 1039 molecules per cell in liver and intestine, respectively, in C3H mice and 762 and 952 molecules per cell in C57BL mice. ApoB mRNA levels were 66 and 170 molecules per cell in the liver and intestine of C3H and 83 and 243 molecules per cell in C57BL, respectively. ApoA-IV mRNA was found to be 3525 and 2964 molecules per cell in the liver and intestine of female C57BL mice, respectively. LDL receptor mRNA levels were 39, 32 and 14 molecules per cell in the liver, intestine and adrenals of C3H.