Modulation of tropoelastin production and elastin messenger ribonucleic acid activity in developing sheep lung

Abstract

During fetal development of sheep lung, elastin content continually increases. For examination of the processes controlling this elastin accumulation, an explant culture system was characterized with respect to changes in tropoelastin production in sheep lung during fetal and early postnatal development. Relative tropoelastin production in cultured lung explants, quantitated by immunoprecipitation, was .apprx. 0.3% of total [14C]valine incorporation during the period from 55 to 104 days after conception. This percentage began to increase by 112 days after conception, reached a maximum value of .apprx. 1.0% by 135 days after conception and then declined to 0.5% soon after birth. The absolute rate of tropoelastin production paralleled these changes in relative tropoelastin production. For evaluation of the processes controlling tropoelastin production in developing sheep lung, total cellular RNA prepared from 68-, 107- and 147-day-old fetal lung was translated in a rabbit reticulocyte lysate system. Elastin mRNA activity, expressed as the amount of elastin precursor translated per microgram of DNA, increased .apprx. 3-fold during fetal lung development, and elastin precursor synthesis, expressed as a proportion of total translational activity, increased in parallel. Apparently, elastin production in developing fetal lung is modulated, at least in part, by the amount of available translatable elastin mRNA present in the tissue.