High adenosine content in human uterine smooth muscle compared with striated skeletal muscle

We determined the concentrations of adenosine and some of its catabolic products in biopsy specimens from predetermined loci of human myometrium under different functional conditions to compare uterine muscle with rectus abdominis muscle from the same individuals. In order to achieve a good resolution in the separation of nucleosides and purine bases, a preseparation procedure was developed prior to analysis of these compounds on high performance liquid chromatography. Adenosine occurred in a nearly 70-fold higher concentration in smooth uterine muscle in comparison with striated skeletal muscle. Similarly, myometrial inosine and hypoxanthine were 7- and 2.4-times in excess over the rectus muscle, whereas xanthine was scarcely and rather evenly represented in the two types of muscles. The uterine content of adenosine and inosine was distinctly higher in pregnant women compared to non-pregnant ones. A regional difference existed for adenosine, with 3.3 times higher concentration in fundus uteri compared to the isthmic part. A reverse pattern was observed for hypoxanthine and inosine, being 2–3 times more frequent in the isthmic part. The orthophosphate concentration was not stoichiometrically related to the adenosine concentration in a simple way, being 2–3 times lower in uterine muscle compared to the skeletal muscle. A significant correlation existed between uterine contents of AMP and adenosine and similarly, significant inverse correlations were apparent between uterine ATP and ADP contents and energy charge on one hand and adenosine content on the other.