DEVELOPMENTAL-CHANGES IN RAT CARDIAC DNA, RNA AND PROTEIN TISSUE BASE- IMPLICATIONS FOR THE INTERPRETATION OF CHANGES IN GENE-EXPRESSION

During cardiac development the expression levels of many genes change as determined by Northern blot, dot blot, RNase protection, quantitati ve RT-PCR, Western blot or immunoprecipitation analyses. It is not alw ays realized that the total amount of RNA or protein per gram of heart , dubbed tissue base, may change significantly during development as w ell, If this would be the case, this has to be taken into account. So far, the (changing) tissue base has not been established during cardia c development. To this end developmental profiles of cardiac DNA, RNA and protein concentration were determined in rats ranging in age from embryonic day 13 until neonatal day 121. The profiles show significant development changes in each parameter, that closely match the distinc t growth phases of the developing heart and provide the parameters tha t are essential for an adequate interpretation of changes in the amoun t of a distinct mRNA and/or protein. In a comparison between in situ h ybridization and Northern blot analysis it is demonstrated that the sa me developmental profile leads to an almost opposite conclusion depend ing on whether or not the changing tissue base is taken into account. These findings are of great interest for studies aimed at unravelling the molecular mechanisms underlying the regulation of gene expression during cardiac development. (C) 1997 Academic Press Limited.