Smooth muscle stretch-activated phospholipase C activity.
Rabbit aortic muscles were stretched from a holding length of 0.6 maximum length (Lmax) to lengths as great as 1.0 Lmax and the new length maintained. When muscles were stretched to 1.0 Lmax, inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] and inositol 1,4-bisphosphate [Ins(1,4)P2] contents were increased at 375 ms (uncorrected for freezing time) poststretch to 209 +/- 27 and 139.8 +/- 12% (SE), respectively, of control values. Increases in Ins(1,4,5)P3 and Ins(1,4)P2 contents reached an apparent maximum at approximately 500 ms, i.e., to 243.7 +/- 15.8 and 180.9 +/- 16.2% of control, and were decreased to near control levels at 1,700 ms poststretch. The stretch threshold for phospholipase C (PLC) activation was 0.85 Lmax. The latency to onset of PLC activation, correcting for the time for freezing, was 275 to 375 ms. Maximal PLC activity was 91 pmol.s-1.100 nmol total lipid P(i)-1, which corresponded to 10% of total phosphatidylinositol bisphosphate being hydrolyzed per second. The mechanism of stretch-activated PLC activity involved influx of Ca2+ via gadolinium-sensitive ion channels, but not via nifedipine-sensitive ion channels.
Matsumoto
H
H
Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia 19104.
Baron
C B
CB
Coburn
R F
RF
D000818:Animals; D002118:Calcium / Q000378:metabolism; D004789:Enzyme Activation; D005615:Freezing; D005682:Gadolinium / Q000494:pharmacology; D066298:In Vitro Techniques; D007295:Inositol Phosphates / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000201:enzymology*; D009638:Norepinephrine / Q000494:pharmacology; D009994:Osmolar Concentration; D011817:Rabbits; D013997:Time Factors; D010738:Type C Phospholipases / Q000378:metabolism*; D014664:Vasodilation / Q000502:physiology*
D007295:Inositol Phosphates; D005682:Gadolinium; D010738:Type C Phospholipases; D002118:Calcium; D009638:Norepinephrine