THE GENETIC HYPERTENSIVE RAT OF LYON STRA IN, LH, AND THE SHR HAVE DISTINCT PROFILES OF TROPOELASTIN AND COLLAGEN TYPE-III EXPRESSION DURING POSTNATAL-DEVELOPMENT OF THE AORTA

Experimental pharmacology and studies on hypertension frequently use g enetically hypertensive animal models like the SHR or the Lyon hyperte nsive rat LH. In order to further characterize these two models we mea sured the expression levels of three major extracellular matrix compon ents in the aortic wall, tropoelastin (TE) and type I and type III col lagen, during postnatal development. The type I collagen expression de creases progressively during the first twelve weeks of postnatal devel opment without significant differences between SHR and LH, or their no rmotensive controls, WKY or LN respectively. No differences were detec ted either for the expression levels of TE and type III collagen betwe en the hypertensive strains and their respective controls. However, di rect comparison of the two hypertensive strains SHR and LH, revealed a specific, strong increase of TE and type III expression for the LH at 5 and 12 weeks (p < 0.001 and 0.005 respectively). The evolution of t he ratios of expression levels between the two collagens (type III/typ e I) on one side and of TE and collagen type I (TE/type I) on the othe r side were similar for the hypertensive strains and their respective controls, but diverged significantly for LH and SHR animals (up to p < 0.001 depending on the age group). Both indicators, III/I and TE/I, a re considerably higher in LH compared to SHR from 5 weeks of post-nata l development onwards. Our results indicate that the genes for TE and type I and III collagen are regulated during postnatal development of LH and SHR. It is however not possible at this point to establish a li nk between mRNA levels and hypertension in these animals. Nevertheless , the ratios III/I and TE/I seem to be good phenotypic markers for the characterisation of LH and SHR strains.