Pretreatment with Porcine Relaxin and Mg Ions Enhances Inhibitory Effects of Dibutyryl Cyclic AMP in Longitudinal Muscle of Estrogen-Treated Rat Myometrium

Abstract

Phasic contractions were evoked in Mg-free Krebs solution by electrical stimulation in the longitudinal myometrial strip taken from estrogen-treated rats, and the application of 30 μM dibutyryl cyclic AMP (db cAMP) for 15min depressed the amplitude of contraction to 81 ± 18% (± SD, n = 23) of the control. The contractile depression caused by db cAMP was not significantly altered by pretreatment with either 1 mM Mg (40min) or 100mU porcine relaxin (15min) alone; however it was markedly enhanced to 22±30% (n=7) of the control response by the combined pretreatment with Mg and relaxin. The enhancement lasted for longer than 2h thereafter in Mg-free Krebs solution. It was discussed that some memory factor was induced by relaxin in the presence of 1 mM Mg to respond strongly to db cAMP. © 1994, PHYSIOLOGICAL SOCIETY OF JAPAN. All rights reserved.