TPA- and agonist-induced force development in myometrium from pregnant and non-pregnant rats.
In myometrium from pregnant rats, 100 nM-TPA elevated resting tension and initially slightly enhanced the contraction induced by 138 mM-KCl. After 20 min this force development significantly declined. In saponin-treated skinned myometrial cells from pregnant rats, 100 nM-TPA enhanced the contraction induced by 0.3 microM-Ca2+, but reduced that induced by 1 microM-Ca2+. These findings suggest that the excitatory and inhibitory actions of TPA on the myometrium are probably due to its action on the contractile proteins. In myometrium from non-pregnant rats, TPA affected neither the resting tension, nor the amplitude of the evoked contractions, nor the Ca2+-induced contractions in skinned myometrium. While TPA only affected tension development in pregnant rats, both 1 mM-carbachol and 90 nM-oxytocin induced a tonic contraction in Ca-free solution independently of the hormonal status of the rats. The latter finding makes it unlikely that activation of protein kinase C is involved in the agonist-induced tonic force development in Ca-free solution.
Missiaen
L
L
Laboratorium of Physiology, K.U.Leuven Campus Gasthulsberg, Belgium.
Kanmura
Y
Y
Eggermont
J A
JA
Casteels
R
R
D000818:Animals; D002217:Carbachol / Q000494:pharmacology*; D005260:Female; D066298:In Vitro Techniques; D009215:Myometrium / Q000187:drug effects / Q000502:physiology*; D010121:Oxytocin / Q000494:pharmacology*; D011189:Potassium Chloride / Q000494:pharmacology*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D051381:Rats; D012016:Reference Values; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014590:Uterine Contraction / Q000187:drug effects*
D010121:Oxytocin; D011189:Potassium Chloride; D002217:Carbachol; D013755:Tetradecanoylphorbol Acetate