Extent of differentiated gene expression in the human endothelium-derived EA.hy926 cell line.

Vascular endothelial cells perform many differentiated functions in processes such as angiogenesis, hemostasis, and inflammation. The number of recognized differentiated functions has increased rapidly in recent years, but there may be many more still unrecognized. The purpose of this study is to estimate the fraction of differentially expressed mRNA in a continuous human endothelium-derived cell line, EA.hy926. Random cDNA clones representing mRNAs from this cell line were labeled and used to probe blots of RNA from EA.hy926 cells and from cells of a relatively undifferentiated line. Of 49 random cDNAs, 5 cDNAs or 10% were found to represent mRNAs that are differentially expressed in EA.hy926 and in early passage umbilical vein endothelial cells. Since more than 10(4) different genes are thought to be expressed in the typical mammalian cell, our data indicate that about 10(3) gene products contribute to the differentiated properties of endothelial cells.

Influence of litter size on antepartum serum relaxin and progesterone immunoactivity levels and on birth in the rat.

In the rat, the antepartum elevation of serum relaxin levels consists of two phases separated by a 24-h interval. The second phase, which occurs between 36 and 24 h before birth, is temporally closely associated with functional luteolysis. Relaxin levels then decline throughout the last approximately 24 h of pregnancy. We have postulated that the two phases in the antepartum elevation of serum relaxin levels may be indicative of an increasingly effective endogenous circadian luteolytic process. There is limited evidence that both luteolysis and birth are delayed in rats with small litters. The present study investigated in detail the relationship between litter size and the timing of both functional luteolysis and birth in rats. The number of conceptuses (C) in Sprague-Dawley-derived rats was surgically adjusted on day 8 of pregnancy (day 8) so that rats bore one, two, three, five, or a full complement (FC) of eight or more C. Rats were maintained under a photoperiod regimen of 14 h of light and 10 h of darkness (lights on from 2100-1100 h) beginning on day 8 and observed for birth at 10-min intervals from 2100 h on day 22. Serum levels of both relaxin and progesterone were determined in blood samples obtained at 4-h intervals from 2400 h on day 19 until birth. Ninety-five percent of the rats that had five or more C gave birth during the light phase on day 23, which was designated the normal birth interval. However, only 20% of the rats with three C or less, gave birth during the normal birth interval, and 47% gave birth about 24 h later during the light phase on day 24, which was designated the late birth interval. The 24-h delay in birth of rats with small litters which delivered during the late birth interval appears to be attributable to a delay in functional luteolysis; the antepartum decline in serum relaxin and progesterone levels occurred about 24 h later in these rats than in rats that delivered during the normal birth interval. It is concluded that the C may be associated with the luteolytic process and thereby influence the time of birth in rats. Additionally, the results of this study are consistent with our hypothesis that there is an endogenous circadian luteolytic process in rats during the antepartum period.