Relaxin affects the shape of rat myometrial cells in culture

The shape of rat myometrial cells in culture was altered by exposure to hormones. Oxytocin (107 microU/ml) significantly decreased mean cell length and area. Treatment of oxytocin-treated cells with relaxin (1.5 micrograms/ml), isoproterenol (10 microM) or (Bu)2 cAMP (1 mM) for 15 min resulted in a significant increase in cell length and area. The effect of relaxin was time dependent, with a significant increase in cell length by 1 min and in cell area by 3 min. Relaxin elicited a concentration-dependent increase in cell length and area between 0.1 and 2 micrograms/ml. The actions of relaxin correlate in time course and concentration dependence with its effects on cAMP elevation in the presence of 0.4 microM forskolin and on changes in myosin light chain kinase kinetic parameters in these cells. Myometrial cells in culture constitute a useful model system in which to correlate physical and biochemical effects of relaxin and other hormones.