Effects of Theophylline on Small Human Placental Arteries in Vitro

Publisher Website
Google Scholar
Abstract
Effects of theophylline on contractions induced by relevant physiological agents in tubular segments of small human placental arteries were measured in an isometric myograph. Theophylline 10-7-3 x 10-3 M caused marked relaxation of steady contractions produced by prostaglandin F2.alpha. (PGF2.alpha.), PGE2 (PGE2), vasopressin or potassium. EC50 for theophylline relaxation of the PGF2.alpha.-contraction was 1.6 x 10-4 M. Emax was 91.5% relaxation. Theophylline was less potent in relaxing the K induced contraction. Pretreatment experiments with 10-4 and 10-3 M theophylline showed a pronounced decrease in contractile Emax-values for PGF2.alpha., PGE2 and vasopressin as a possible indication of non-competitive antagonism. The results motivate further studies to elucidate possible effects of theophylline and other xanthines on the vascular resistance and blood flow in placenta. A vasodilating action combined with uterine relaxation could possibly increase placental blood flow and be of therapeutic interest in relation to intrauterine growth retardation, which is an important problem in perinatology.