Postpartum changes in the mechanical responses of the circular muscle of rat uterus.
The circular muscle strips were isolated from rat uterus 10-60 h after parturition, and the electrical and mechanical responses were investigated. The muscle strips exhibited a variety of contractile activity ranging from frequent spontaneous contractions generated on an elevated muscle tone to a sustained contracture, when incubated with Mg-free Krebs solution. The muscle tone was lowered, and phasic contractions were abolished when the external Ca was removed. Muscle tone was also lowered by addition of 1.2 mM Mg, 1 mM spermidine, or 1 mM tetracaine. The membrane potential was about -25 mV in a muscle which exhibited a contracture, and the membrane was hyperpolarized by 20-25 mV by the (1.5-4.5 x 10(-5) M) caused a gradual decrease in muscle tone, and the that Ca-influx was increased, for which prostaglandin(s) was membrane was hyperpolarized. In view of the above results, it is hypothesized that Ca-influx was increased, for which prostaglandin(s) was probably responsible, in the circular muscle of postpartum rat uterus, thereby elevating the muscle tone in Mg-free solution.
Osa
T
T
Department of Physiology, Yamaguchi University School of Medicine, Ube, Japan.
Maruta
K
K
D000818:Animals; D002118:Calcium / Q000378:metabolism; D005260:Female; D007213:Indomethacin / Q000494:pharmacology; D007552:Isotonic Solutions / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D009130:Muscle, Smooth / Q000502:physiology*; D049590:Postpartum Period; D011247:Pregnancy; D051381:Rats; D013095:Spermidine / Q000494:pharmacology; D013748:Tetracaine / Q000494:pharmacology; D014590:Uterine Contraction / Q000187:drug effects
D007552:Isotonic Solutions; C051865:Krebs-Ringer solution; D013748:Tetracaine; D008274:Magnesium; D002118:Calcium; D013095:Spermidine; D007213:Indomethacin