The mechanical response of the isolated longitudinal muscle of pregnant rat myometrium to adenosine triphosphate in the Ca-free solution containing various polyvalent cations.
A small tonic contraction could be evoked by 3 mM adenosine triphosphate (ATP) in the longitudinal muscle of pregnant rat myometrium which was incubated with the Ca-, Mg-free solution containing 2 mM EGTA (40 mM K). The amplitude of the tonic contraction was decreased by exposure to the solution within a few hours, but was again increased when 1-10 mM Mg was added to the Ca-free solution. The ATP-induced contraction was increased for more than 7 h during exposure to the Ca-free solution containing Mg ions. The ATP-induced contraction in the Ca-free (Mg-free) solution was also produced when the solution contained 1 mM Mn or 1.5 mM La. On the other hand, the tonic contraction evoked by 1 mM Ca or Ba in the presence of 40 mM K was depressed by ATP. The above results led us to propose that the ATP-induced contraction evoked in the Ca-free solution containing Mg was mediated by a process independent of Ca, and possibly mediated by a translocation of Mg in the cell. La and Mn could take the place of Mg in producing a tonic contraction caused by ATP application.
Osa
T
T
Department of Physiology, Yamaguchi University School of Medicine, Ube, Japan.
Maruta
K
K
D000200:Action Potentials; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D004558:Electric Stimulation; D005260:Female; D066298:In Vitro Techniques; D007811:Lanthanum / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D010477:Perfusion; D011188:Potassium / Q000494:pharmacology; D011247:Pregnancy; D051381:Rats; D011919:Rats, Inbred Strains; D014590:Uterine Contraction / Q000187:drug effects*
D002110:Caffeine; D008345:Manganese; D007811:Lanthanum; D000255:Adenosine Triphosphate; D008274:Magnesium; D011188:Potassium